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Biomedical subjects

D L Miller

Publications and source records attributed to D L Miller.

At least 289 records · Page 16Linked to original sources
PubMed1990

The influence of variations in biophysical conditions on hemolysis near ultrasonically activated gas-filled micropores.

Hemolysis induced by 1.9-MHz ultrasound in 0.5% suspensions of canine erythrocytes with 3.7-microns-diam micropore-trapped gas bodies was investigated for a variety of biophysical conditions. For isotonic media, hemolysis increased with exposure duration (4-64 min) but did not greatly change with exposure temperature (15, 25, 37, and 48 degrees C), or prior heat treatment (48 or 50 degrees C for 30 min). The temperature results were especially interesting because increased temperatures might have been expected to increase the sensitivity of the cells to the ultrasonically activated gas bodies. Variations in osmolarity (180, 290, or 580 mOsm) had little influence on the results. Increasing the viscosity (0.7, 2.2, 2.3, or 4.2 cP) of the medium decreased the effect, and this did not seem to depend on the molecular weight of the dextran additive (9400 or 250,000). A medium with elevated mass density (1.12 g/cm3) seemed to increase the effectiveness of the exposures. This condition eliminated the density difference between the cells and the medium, and might have been expected to reduce the effectiveness of the exposures, because the radiation force, which theoretically gathers cells to the gas bodies, is minimized for such conditions. This information should aid in developing refinements to the theoretical understanding of low-intensity ultrasonic bioeffects.

Animals↗
PubMed1990

Rotavirus serotypes 6 and 10 predominate in cattle.

Calf fecal rotavirus strains were serotyped in enzyme-linked immunosorbent assays, using monoclonal antibodies to the VP7s of serotypes 1, 2, 3, 5, and 6 and to the VP4 of B223 (designated serotype 10). Sixty-six percent of 162 samples were typed as serotype 6, and 7% were serotyped as serotype 10. Most of the untyped strains did not react with a monoclonal antibody directed to a common VP7 epitope, indicating insufficient virus present in the samples. However, seven untyped samples that did react with this antibody were adapted to culture and typed, and six of these also proved to belong to serotype 6 or 10. Two of these viruses belonged to a monotype within serotype 6 that did not react with the serotype 6 monoclonal antibody. The seventh isolate reacted in cross-neutralization tests with serotype 8 viruses. Bovine rotaviruses from the United Kingdom, Federal Republic of Germany, and Japan that had been shown previously to be distinct from serotype 6 were compared in neutralization tests with B223 from the United States. These viruses proved to be a closely reacting group distinct from all other rotavirus serotypes, justifying the establishment of serotype 10 as the second major type of bovine rotavirus.

Animals↗
PubMed1990

An update on HIV-testing at a London sexually transmitted diseases clinic: long-term impact of the AIDS media campaigns.

Trends in the number of tests for HIV-1 antibody at a London sexually transmitted diseases clinic showed substantial changes between September 1985 and June 1988. From an average of 100 tests per month between September 1985 and August 1986, the average increased to 365 tests per month for September 1986 to August 1987. This levelled off at 243 tests per month between September 1987 and June 1988. The average number of positive tests per month between September 1985 and June 1988 remained constant, though the number of seropositive tests in females increased. Male and female populations displayed similar temporal patterns. The greatest increase was seen in the tests generated by heterosexual males and females with no other risk factors. This group generated 42% of the 8012 tests performed during the study period. The Clinic's catchment area predominantly included London and surrounding areas and temporal patterns were similar for residents from each of the Thames Regions. The temporal patterns observed coincided with periods of increased media attention on HIV infection/AIDS and involved campaigns by the popular press, television, Department of Health Education Authority. The increase in tests during the time of maximum media exposure, the subsequent plateau at a level substantially higher compared with the period preceding the media campaigns and the large increase in heterosexual males and females tested, all suggest that the campaigns have contributed to increasing awareness of HIV infection/AIDS as a major contemporary public health problem.

AIDS Serodiagnosis↗
PubMed1990

Gastrinomas: localization by means of selective intraarterial injection of secretin.

Small doses (30 U) of secretin were injected directly into the splenic, gastroduodenal, hepatic, and superior mesenteric arteries of 13 patients with Zollinger-Ellison syndrome who were undergoing angiography to localize gastrin-secreting tumors of the islet cells. Blood samples from the right hepatic vein and a peripheral vein were drawn before and 30, 60, 120, and 210 seconds after each intraarterial secretin (IAS) injection. A 50% rise in gastrin level in the 30-second sample from the hepatic vein localized the gastrinoma to the head, body, or tail of the pancreas, depending on the artery into which secretion was injected. IAS results were positive in seven of 13 patients (54%); selective angiography was positive in five of 13 (38%); and the combined study, selective angiography with IAS injection, was positive in 10 of 13 (77%). Portal venous sampling was positive in six of 13 (46%). Selective IAS injection, combined with angiography, is the most sensitive study for localizing gastrinomas and avoids percutaneous transhepatic catheterization for portal venous sampling.

Adult↗
PubMed1990

Petrosal sinus sampling: discordant lateralization of ACTH-secreting pituitary microadenomas before and after stimulation with corticotropin-releasing hormone.

Petrosal sinus sampling was performed 171 times in 157 patients with known or suspected Cushing disease. In all cases, samples for measuring adrenocorticotropic hormone (ACTH) levels were obtained from both inferior petrosal sinuses and a peripheral vein, both before and after intravenous corticotropin-releasing hormone (CRH) administration. In seven examinations in seven patients, a ratio, or gradient, between the ACTH levels in the inferior petrosal sinuses existed in the samples obtained prior to CRH stimulation; however, poststimulation samples demonstrated reversal of the gradient, suggesting lateralization to the contralateral side of the pituitary gland. Data from surgical exploration of the pituitary gland were available for six of these patients, all of whom had adenomas. Prestimulation samples provided correct lateralization in three patients, and in two patients the poststimulation samples provided correct lateralization. One patient had a midline adenoma. When the results of pre- and poststimulation petrosal sinus sampling conflict, neither can be relied on uniformly to provide correct lateralization of ACTH-secreting pituitary adenomas.

Adenoma↗
PubMed1990

Fluorescence-guided laser-assisted balloon angioplasty in patients with femoropopliteal occlusions.

In 12 patients (aged 64 +/- 10 years) with femoropopliteal occlusions (1-27 cm; average, 8.4 cm length) that could not be recanalized by standard guidewire-balloon angioplasty techniques, percutaneous laser-assisted balloon angioplasty was performed by use of a new fluorescence-guided dual-laser system. Plaque detection by 325-nm laser-excited fluorescence spectroscopy provided real-time feedback control to a 480-nm pulsed dye laser (2-microseconds pulses) for atheroma ablation. By means of a common 200-microns optical fiber, after diagnostic fluorescence sensing, computer algorithms directed a fire or no-fire signal (5 Hz) to the treatment laser for selective plaque removal. Laser recanalization (15-50 mJ/pulse) was successful in 10 of 12 patients; this procedure was followed by definitive balloon angioplasty in seven of 12 patients with increased ankle/arm indexes (from 0.60 +/- 0.12 at baseline to 0.84 +/- 0.11 after treatment, p = 0.0043). In laser and balloon angioplasty failures, all femoropopliteal occlusions were heavily calcified, and there were two mechanical guidewire perforations without clinical sequelae. Ablation of calcified lesions required higher pulse energies and greater total energy per centimeter of recanalized tissue (1,837 +/- 1,251 mJ/cm vs. 90 +/- 39 mJ/cm, p = 0.0036). Fluorescence spectroscopy (n = 219 sites) was helpful in flush occlusions and correctly identified plaque, underlying media, and thrombus by changes in fluorescence intensity, shape, and peak position. Thus, when fluorescence-guided laser angioplasty was used in a subgroup of patients refractory to standard angioplasty techniques, primary recanalization and subsequent balloon angioplasty of femoropopliteal occlusions was successful in 83% and 58% of the patients, respectively. Importantly, treatment of heavily calcified lesions accounted for all of the failures and will require modified delivery systems to create larger primary channels and to increase catheter-tip control, which should improve clinical results in the future.

Adult↗
PubMed1990

The diagnosis of acromegaly: value of inferior petrosal sinus sampling.

The early diagnosis of acromegaly may be difficult when serum levels of growth hormone are minimally elevated and imaging of the pituitary gland fails to show an adenoma. However, transsphenoidal surgery has the greatest chance of cure at this stage. We therefore investigated the value of sampling petrosal sinuses for measurement of growth hormone in this group of patients. Simultaneous bilateral sampling of the inferior petrosal sinuses to measure serum concentrations of growth hormone was performed in five patients suspected of having acromegaly but with nondiagnostic CT scans (n = 5) and MR images (n = 3) of the pituitary gland. Levels of growth hormone from the petrosal sinuses were five to 36 times greater than levels in the peripheral veins in all five patients, and three of four showed a marked response to growth hormone-releasing hormone. During transsphenoidal surgery, growth hormone-producing microadenomas were resected completely in four patients. In the fifth patient, a left-sided microadenoma had invaded the cavernous sinus and could not be resected completely. Lateralization of the adenomas within the pituitary gland on the basis of differences in levels of growth hormone between the two petrosal sinuses was not completely reliable. Elevated levels of growth hormone in selective samples from the inferior petrosal sinuses can help support an early diagnosis of acromegaly when peripheral growth hormone levels and imaging are not diagnostic.

Acromegaly↗
PubMed1990

A new feeder for powdered diets.

A new feeder for powdered diets was developed for use with small rodents. The feeder has unique advantages over commercially available feeders. Wastage is minimal, food intake can be measured, and it is adaptable to various rodent species and different types of powdered diets. This study describes and evaluates the new feeder using three animal groups--weanling rats, adults rats, and adult hamsters. In the rat studies, the rate of growth of weanling and adult rats fed commercial rat chow in pellet form using conventional feeders was the same as that of rats fed the same chow in meal form using the new feeders. Likewise in the hamster studies, the rate of growth of adult hamsters fed powdered semi-synthetic diet from conventional glass jars was the same as those fed the same diet from the new feeders. The new feeders supplied the animals with a continuous supply of meal free of contamination from feces or urine. Unrecoverable spillage (wastage) was 1-2% of the amount of food given. The new feeders were easy to handle and clean, had ample capacity, and needed little attention.

Animal Feed↗
PubMed1990

Reentry: manpower issues related to nonpracticing dental hygienists.

At the present time there is concern about the current and projected dental hygiene manpower situation. As applicant pools diminish and dental hygiene schools close, the need to investigate retention and reentry issues for hygienists increases. The purpose of this study was to determine (1) the number of unemployed dental hygienists who could be enticed to reenter the workforce, (2) the reasons why these dental hygienists left their profession, and (3) the factors that could facilitate their reentry into dental hygiene. A random sample of 10,249 licensed dental hygienists in 27 states was surveyed. Only nonpracticing dental hygienists completed the questionnaire; practicing dental hygienists returned the questionnaire unanswered. A 65% response rate was established. Of those dental hygienists returning questionnaires, 79% (N = 4,665) were currently practicing and 21% (N = 1,227) were not practicing. Of those hygienists who were not practicing, 63% (N = 773) stated intentions of returning to the work force if circumstances change. Within the unemployed sample, a subsample was created consisting of nonpracticing hygienists who have been out of the work force for less than eight years but intend to return to dental hygiene. Data were analyzed using frequency distribution, chi-square analyses, and factor analyses. Results showed five major reasons cited for leaving dental hygiene: (1) family responsibilities, (2) boredom, (3) fear of infectious disease, (4) lack of benefits, and (5) lack of adequate salary.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Current patterns of the use of heparin in angiography].

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.

Adult↗
PubMed1989

Structure and transcription of the mitochondrial genome in heteroplasmic strains of Saccharomyces cerevisiae.

Saccharomyces cerevisiae strain FF1210-6C/170 is respiratory deficient due to a mutation of the penultimate base of the mitochondrial tRNA(Asp) gene. We have identified a number of progeny from this strain which have reverted to respiratory sufficiency by the excision and tandem amplification of a small region of the mitochondrial (mt) DNA carrying the tRNA(Asp) gene, while also maintaining the full-length mtDNA. We have studied the structure of the mtDNA and mitochondrial transcription in a number of these heteroplasmic strains. The exact site of the recombination involved in the excision of the repeating unit of the amplified mtDNA has been determined for five of the revertants. Recombination occurs between identical sequences 4-13 base pairs in length. Each of the different repeating units of the amplified DNA retains an active promoter which has been moved to a site just upstream of the tRNA(Asp) gene by the excision/amplification. Transcripts from the heteroplasmic strains have been characterized to determine the sites of mitochondrial RNA termini. We find that in addition to the 5' and 3' processing of the tRNAs, many of the transcripts terminate at a position about 300 base pairs downstream of the gene for tRNA(Asp). We also find that 3' processing of tRNA(Asp) precursors is absent in petite strains which lack 5' processing indicating that 5' processing of tRNA(Asp) may be a prerequisite for 3' processing in this mutant.

Base Sequence↗
PubMed1989

Site-directed mutagenesis of the GDP binding domain of bacterial elongation factor Tu.

The tertiary structure model of EF-Tu predicts that the amino acid sequence Val-Asp-His-Gly-Lys-Thr-Thr-Leu (residues 20-27) forms a pocket that binds the pyrophosphate group. To test this model we used site-directed mutagenesis to produce forms of EF-Tu altered in this region. The following mutations were constructed: Gly-20, Val-23, Glu-24, Ile-25, and Pro-27. Each protein was labeled with [35S]Met and was tested for its ability to interact with guanosine nucleotides and EF-Ts. The in vivo activity of each altered protein was tested by determining its ability to confer aurodox sensitivity to a resistant host. Mutations at residues 23, 24, 25, and 27 eliminated the ability of EF-Tu to interact with either guanosine nucleotides or EF-Ts in vitro, and these forms were also inactive in vivo. In contrast, the Gly-20 form was nearly as active as wild-type EF-Tu in vitro and in vivo. This mutation is theoretically equivalent to reversion of the Gly to Val transforming mutation of the cellular form of the ras gene product p21, a protein proposed to be structurally similar to EF-Tu in the GDP binding domain. In contrast to its effect in the ras gene, the Val to Gly conversion did not affect the endogenous GTPase of EF-Tu. We conclude that the tertiary structure model is correct in its assignment of the pyrophosphate binding site to residues 23-27; however, there are likely to be some significant differences between the configurations of the GTPases of EF-Tu and p21.

Amino Acid Sequence↗
PubMed1989

Mutagenesis of bacterial elongation factor Tu at lysine 136. A conserved amino acid in GTP regulatory proteins.

We have studied the effects of specific amino acid replacements in EF-Tu upon the protein's interactions with guanine nucleotides and elongation factor Ts (EFTs). We found that alterations at the lysine residue of the Asn-Lys-Cys-Asp sequence, the guanine ring-binding sequence, differentially affect the protein's ability to bind guanine nucleotides. Wild type EF-Tu (Lys-136) binds GDP and GTP much more tightly than do many of the altered proteins. Replacing lysine by arginine lowers the protein's affinity for GDP by about 20-fold relative to the change in its affinity for EF-Ts. Substitutions at residue 136 by glutamine (K136Q) and glutamic acid (K136E) further lower the protein relative affinity for GDP by factors of about 4 and 10, respectively. In contrast, replacement of the residue by isoleucine (K136I) eliminates guanine nucleotide binding as well as EF-Ts binding. Apparently, the distortion of this loop by substitution at residue 136 of a bulky hydrophobic residue can hamper the binding for both substrates or disrupt the folding of the protein. All altered proteins except EF-Tu(K136I) are able to bind tRNA(Phe); however, they require much higher concentrations of GTP than wild type EF-Tu. In minimal media, Escherichia coli cells harboring plasmids encoding EF-Tu(K136E) or EF-Tu(K136Q) suffer growth retardation relative to cells bearing the same plasmid encoding wild type EF-Tu. Co-transformation of these cells with a compatible plasmid bearing the EF-Ts gene reverses this growth problem. The growth retardation effect of some of the altered proteins can be explained by their sequestering EF-Ts. These results indicate that EF-Ts is essential to the growth of E. coli and suggest a technique for studying EF-Ts mutants as well as for identifying other guanine nucleotide exchange enzymes.

Amino Acid Sequence↗