Biomedical subjects

D W Miller

Publications and source records attributed to D W Miller.

At least 109 records · Page 6Linked to original sources

PubMed1996

Metabolism of 2-amino-alpha-carboline. A food-borne heterocyclic amine mutagen and carcinogen by human and rodent liver microsomes and by human cytochrome P4501A2.

2-Amino-alpha-carboline (A alpha C) is a mutagenic and carcinogenic heterocyclic amine that is formed as a pyrolysis product during the high temperature cooking of food and the burning of tobacco. Human, rat, and mouse hepatic microsomes each catalyzed the NADPH-dependent oxidation of A alpha C to form six products separable by HPLC. The two major metabolites, which together accounted for approximately 85% of the total metabolism, were characterized by UV, fluorescence, proton magnetic resonance, and mass spectral analyses as 3-hydroxy-A alpha C and 6-hydroxy-A alpha C. The remaining 15% were judged to be N-hydroxy-A alpha C and its oxidation products, based on chromatographic and spectral comparisons with a standard, whose synthesis and characterization are also described. Although the proportions of each metabolite were similar across species and individuals, the overall rate of metabolism of A alpha C by human hepatic microsomes showed a wide interindividual variation (37-fold), with a mean activity that was comparable with that observed with rat or mouse liver microsomes. alpha-Naphthoflavone, a selective inhibitor for cytochromes P4501A1 and P4501A2, strongly inhibited formation of both ring-hydroxylation and N-oxidation products by human, rat, or mouse liver hepatic microsomes. In addition, A alpha C oxidation was strongly correlated (r = 0.98; p < 0.001) with the oxidation of 4-aminobiphenyl, a known selective substrate for human and rodent cytochromes P4501A2. Immunoblot analyses confirmed the presence of cytochromes P4501A2, and not P4501A1, in human liver microsomes. Additional studies using recombinant human cytochromes P450 show that high catalytic activity for A alpha C metabolism was associated with human cytochrome P4501A2. Lower, but significant activity was also noted for P4501A1 and P4502C10, which could have important implications for the metabolic activation of A alpha C extrahepatic tissues. Neither A alpha C metabolism nor immunoreactive cytochrome P4501A2 (or P4501A1) was detected in human pancreatic microsomes. Although further carcinogenicity and biomarker studies for A alpha C are needed, the high rate of A alpha C metabolism by human liver cytochrome P4501A2 suggests that humans with the rapid P4501A2 phenotype with may be more susceptible than rodents to this heterocyclic amine carcinogen.

Animals↗

PubMed1996

Protein synthesis and secretion by the rat seminiferous tubule in vivo not affected by experimental varicocele.

PURPOSE: Varicocele is associated with testicular dysfunction and male infertility. In vivo protein synthesis and secretion by the seminiferous tubules can be studied as an overall assessment of Sertoli cell function. The present experiments were undertaken to determine the effect of experimental left varicocele (ELV) on seminiferous tubule protein synthesis and secretion. MATERIALS AND METHODS: Androgen binding protein (ABP) was determined in native testicular interstitial fluid by radioimmunoassay. 35S-methionine was perifused around seminiferous tubules in vivo in testes of control rats and those with 30 day ELV. Interstitial fluid (IF) and lumen fluid (LF) were subsequently collected by micropuncture, and a tubule extract (TE) was prepared. Proteins in all fluids were subjected to one- and two-dimensional electrophoresis and autoradiography to evaluate the total synthesized proteins (those in TE) as well as the secreted proteins (those in LF). RESULTS: Two-dimensional electrophoresis allowed detection of approximately 170 proteins synthesized by the seminiferous tubules in vivo with 60 of those being secreted into the tubule lumen within a 3-hour time period. Experimental left varicocele significantly reduced the concentration of a specific protein, ABP, in ipsilateral interstitial fluid, but more extensive evaluation of protein synthesis and secretion into the tubule lumen did not corroborate a significant change in protein synthesis and secretion by rat seminiferous tubules under the influence of varicocele. CONCLUSIONS: Experimental varicocele does not significantly alter the panel of proteins synthesized by rat seminiferous tubules and secreted into the lumen in vivo. At this level it does not appear that altered Sertoli cell function is within the primary mechanism of dysfunction subsequent to varicocele.

Animals↗

PubMed1996

Subcutaneous sumatriptan for the treatment of migraine: humanistic, economic, and clinical consequences.

OBJECTIVES: This study examined the humanistic, economic, and clinical consequences of using subcutaneous sumatriptan for 6 months for the acute treatment of migraine in 126 patients enrolled in a group-model health maintenance organization. METHODS: Patients received open-label sumatriptan (6 mg) for the treatment of migraines that occurred during a 6-month period. For each migraine, patients recorded migraine pain severity (none, mild, moderate, or severe) before treatment and 2 hours posttreatment and the time until onset of patient-defined meaningful relief. Patients also completed both the Short Form-36 Health Survey and Migraine-specific Quality of Life (QOL) Questionnaire at screening (to cover the period prior to initiation of treatment) and after 3 and 6 months of treatment. Patients' medical records were reviewed to obtain information on the frequency of migraine-related pharmacy use, general outpatient services, and urgent care services during the treatment period and the 12 months prior to initiation of treatment. RESULTS: By 2 hours after the dose, 71% of patients had moderate or severe pain reduced to mild or none, and 86% of patients achieved meaningful relief. At 3 months and 6 months, sumatriptan was associated with improvements relative to pre-sumatriptan baselines in Short Form-36 Health Survey and Migraine-specific QOL Questionnaire scores (P < .002). Sumatriptan was also associated with significant reductions in the average number of migraine-related general outpatient and urgent care services (P < .001). CONCLUSIONS: The use of sumatriptan for 6 months was associated with improvements in health-related quality of life, reductions in health care resource use, and a high percentage of treatment successes.

Adolescent↗

PubMed1995

Attenuated virulence of chitin-deficient mutants of Candida albicans.

We have analyzed the role of chitin, a cell-wall polysaccharide, in the virulence of Candida albicans. Mutants with a 5-fold reduction in chitin were obtained in two ways: (i) by selecting mutants resistant to Calcofluor, a fluorescent dye that binds to chitin and inhibits growth, and (ii) by disrupting CHS3, the C. albicans homolog of CSD2/CAL1/DIT101/KT12, a Saccharomyces cerevisiae gene required for synthesis of approximately 90% of the cell-wall chitin. Chitin-deficient mutants have no obvious alterations in growth rate, sugar assimilation, chlamydospore formation, or germ-tube formation in various media. When growing vegetatively in liquid media, the mutants tend to clump and display minor changes in morphology. Staining of cells with the fluorescent dye Calcofluor indicates that CHS3 is required for synthesis of the chitin rings found on the surface of yeast cells but not formation of septa in either yeast cells or germ tubes. Despite their relatively normal growth, the mutants are significantly less virulent than the parental strain in both immunocompetent and immunosuppressed mice; at 13 days after infection, survival was 95% in immunocompetent mice that received chs3/chs3 cells and 10% in immunocompetent mice that received an equal dose of chs3/CHS3 cells. Chitin-deficient strains can colonize the organs of infected mice, suggesting that the reduced virulence of the mutants is not due to accelerated clearing.

Animals↗

PubMed1995

Identification and characterization of human beta 2-chimaerin: association with malignant transformation in astrocytoma.

Molecular processes resulting in the malignant transformation from low- to high-grade astrocytoma remain poorly understood. Using reverse transcriptase PCR, we identified a gene that is differentially expressed in normal brain and low-grade astrocytoma compared to glioblastoma tissues. This gene is identical to human beta 2-chimaerin, which encodes a 468-amino acid GTPase-activating protein for p21rac. The gene was localized to human chromosome 7p15.3 by fluorescence in situ hybridization mapping. Human beta 2-chimaerin is expressed in a variety of human tissues, with the highest expression level detected in human brain and pancreas. RNase protection assays indicated that the expression level of this gene is high in all the normal brain and low-grade astrocytoma samples tested compared to malignant gliomas. The down-regulation of beta 2-chimaerin expression in the high-grade gliomas suggests that decreased expression of this gene may be a feature of progression in the development of malignant glioma.

Amino Acid Sequence↗

PubMed1995

Effect of the p-glycoprotein inhibitor, cyclosporin A, on the distribution of rhodamine-123 to the brain: an in vivo microdialysis study in freely moving rats.

The p-glycoprotein is a transmembrane efflux transporter found on the luminal side of the capillary endothelial cells that comprise the blood-brain barrier. This study examined the effect of a p-glycoprotein inhibitor, cyclosporin A, on the distribution to the brain of a p-glycoprotein substrate, rhodamine-123, in freely moving rats using intracerebral microdialysis coupled with on-line HPLC analysis. Results from crossover experiments show that the coadministration of cyclosporin A significantly increased the distribution of rhodamine-123 to the brain. The plasma disposition of rhodamine-123 was unchanged by cyclosporin A, indicating that the change in brain exposure was mediated by a process at the level of the blood-brain barrier, possibly by inhibition of the p-glycoprotein efflux transporter. This finding suggests a functional activity of the p-glycoprotein in the blood-brain barrier and validates an in vivo model to examine the role of this transporter in the brain distribution of drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Analysis of the Wilms tumor suppressor gene WT1 in endometrial carcinoma.

This study reports on the evaluation of the Wilms tumor suppressor gene WT1 in 14 endometrial carcinomas. Despite the fact that several endometrial carcinomas were shown to express WT1, we were unable to demonstrate mutations in the MT1 zinc finger region, suggesting that WT1 does not play a prominent role in the etiology of this malignancy.

Base Sequence↗

PubMed1995

A statistical mechanical model for hydrogen exchange in globular proteins.

We develop a statistical mechanical theory for the mechanism of hydrogen exchange in globular proteins. Using the HP lattice model, we explore how the solvent accessibilities of chain monomers vary as proteins fluctuate from their stable native conformations. The model explains why hydrogen exchange appears to involve two mechanisms under different conditions of protein stability: (1) a "global unfolding" mechanism by which all protons exchange at a similar rate, approaching that of the denatured protein, and (2) a "stable-state" mechanism by which protons exchange at rates that can differ by many orders of magnitude. There has been some controversy about the stable-state mechanism: does exchange take place inside the protein by solvent penetration, or outside the protein by the local unfolding of a subregion? The present model indicates that the stable-state mechanism of exchange occurs through an ensemble of conformations, some of which may bear very little resemblance to the native structure. Although most fluctuations are small-amplitude motions involving solvent penetration or local unfolding, other fluctuations (the conformational distant relatives) can involve much larger transient excursions to completely different chain folds.

Drug Stability↗

PubMed1995

Amphetamine, cocaine, and dizocilpine enhance performance on a lever-release, conditioned avoidance response task in rats.

A lever-release version of the conditioned avoidance response (CAR) task was used to assess the behavioral effects of several psychomotor stimulants in rats. The indirect dopamine agonists, d-amphetamine (0.1 and 0.25 mg/kg) and cocaine (7.5 and 15 mg/kg), enhanced performance on this task. Both drugs increased percent avoidance responses and decreased avoidance latency. A higher dose of amphetamine (0.5 mg/kg) also decreased avoidance latency but failed to improve percent avoidance. Similar effects were seen at low (0.01 and 0.025 mg/kg) and high (0.05 mg/kg) doses of dizocilpine (MK-801), a stimulant that acts as a noncompetitive antagonist of N-methyl-d-aspartate (NMDA) glutamate receptors. When combined with haloperidol (0.1 mg/kg), a dopamine antagonist, amphetamine (0.25 mg/kg) and dizocilpine (0.025 mg/kg) had differential effects on the lever-release CAR task. Thus, amphetamine-haloperidol was significantly better than haloperidol alone on percent avoidance but not on avoidance latency, whereas dizocilpine-haloperidol had the opposite effect: significantly better than haloperidol alone on avoidance latency but not on percent avoidance. Taken together, these results provide further support for dopaminergic mechanisms in CAR performance but suggest an opposing glutamatergic influence.

Amphetamine↗

PubMed1995

Altered metaphase chromosome structure in xrs-5 cells is not related to its radiation sensitivity or defective DNA break rejoining.

The chinese hamster ovary (CHO) cell line xrs-5 is a radiation-sensitive derivative of CHO-K1 cells. The xrs-5 cells have a defect in DNA double-strand break rejoining and show alterations in chromosome structure and nuclear morphology. The relationship between radiation sensitivity and metaphase chromosome morphology was examined in 12 'revertant' xrs-5 clones isolated following treatment with 5-azacytidine. nine of the clones were radioresistant while the other three retained xrs-5-like radiation sensitivity. Chromosome morphology reverted to CHO-K1-like characteristics in three of the radioresistant clones and one of the radiosensitive clones suggesting that the over-condensed metaphase chromosome morphology of xrs-5 cells does not underlie its radiation sensitivity. Radiation sensitivity did correlate with DNA double-strand break rejoining ability. The radioresistant clones showing the over-condensed xrs-5-like chromosome morphology were also slightly more sensitive to the topoisomerase II inhibitor etoposide (VP-16) than CHO-K1, suggesting that the over-condensed morphology might be due to alterations in the phosphorylation of chromatin proteins.

Animals↗

PubMed1995

Deduction of the air w value in a therapeutic proton beam.

Utilization of air-filled ionization chambers with 60Co-based reference calibrations in proton dosimetry requires application of water to air stopping power ratios and the mean energy required to produce an ion pair (W or w). Accepted uncertainties in current w values for protons leads to a dosimetric uncertainty of 4 per cent when ionization chambers are employed to measure absorbed dose. For this reason, proton dosimetry protocols recommend the use of calorimetry as the absorbed dose standard. We used calorimetry in conjunction with an ionization chamber with 60Co reference calibrations to deduce the proton w value in the entrance region of a 250 MeV proton beam: 34.2 +/- 0.5 eV. Application of this w value, with its 1.5 per cent uncertainty, allows determination of dose in therapeutic proton beams, with uncertainties comparable to photon and electron values.

Air↗

PubMed1995

Protein synthesis and secretion by the rat caput epididymidis in vivo: influence of the luminal microenvironment.

The role of intraluminal factors in regulating the functions of the epididymal epithelium is unknown and virtually unexplored. Simultaneous in vivo microperfusion and microperfusion procedures were carried out on rat caput epididymal tubules to examine the effects of the intraluminal microenvironment on protein synthesis and secretion. Caput tubules were perifused with 35S-methionine for 3 h while the tubule lumen was subjected to a stop-flow perfusion of either native caput content from another epididymis (NCC), artificial caput fluid containing no testicular factors (ACF), or rete testis fluid (RTF). Protein synthesis and secretion were measured quantitatively as trichloroacetic acid- (TCA) precipitable 35S-methionine-labeled proteins (cpm/microliter) and qualitatively as autoradiograms of electrophoresed 35S-methionine-labeled proteins. Electrophoresed proteins, i.e., those in fluids collected by micropuncture, were: perifused interstitial fluid (IF), lumen fluid from the perifused but not perfused length of tubule (LF), and the perfusion fluid (PF) re-collected from the tubule lumen. Undiluted tubule extract (TE) of the perfused length of tubule was also analyzed. ACF in the lumen caused a significant reduction in proteins synthesized and secreted by the epithelium, and RTF in the lumen returned protein synthesis and secretion to control values. For example, TCA-precipitable 35S-methionine-labeled proteins in TE of tubules perfused with NCC, ACF, or RTF were 107.6 +/- 13.1, 58.9 +/- 6.9, and 121.9 +/- 19.7 x 10(3) cpm/microliters, respectively. Autoradiograms reinforced this data. Subsequently, tubules were perfused with ACF or ACF containing physiological concentrations of sex hormone-binding globulin (SHBG; an androgen-binding protein [ABP] homolog), 5 alpha-dihydrotestosterone (DHT), or SHBG+DHT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Anabolic steroid use by adolescents: prevalence, motives, and knowledge of risks.

Athletes and nonathletes use anabolic-androgenic steroids (AAS) to improve their strength and enhance their appearance. Few studies have been undertaken in the 1990s to assess the use of AAS in adolescents, following changes in legislation. This study was conducted to determine the prevalence of AAS use by high school students in Denver, Colorado, an area with high sports participation. A confidential questionnaire was completed by 6,930 students (response rate 96.6%) at 10 Denver high schools. The prevalence of AAS use was 2.7% (4.0% for boys and 1.3% for girls). Prevalence was slightly higher in sport participants than nonparticipants. The mean age of starting AAS was 14 years (range 8-17 years). This study is the first documented detailed assessment of high school students' knowledge of the risks of AAS. It shows knowledge deficits regarding potential side effects. Users of AAS were less likely than nonusers to acknowledge the risks of AAS. Only 18% of students claim to have been informed about AAS by physicians. The results suggest that health care providers should provide more information to adolescents about AAS. If educational efforts are found effective, teaching efforts regarding AAS should start in junior high school or sooner and continue through high school.

Adolescent↗

PubMed1995

A review of proton beam radiation therapy.

Beams of protons have been used for radiation treatment for approximately 40 years. This paper provides a short summary of activities from institutions that have contributed to the field over this period. The paper reviews some of the basic interactions of protons with matter that are relevant to radiation treatment and summarizes current knowledge pertaining to the response of biological systems to proton beam radiation. The technical means of producing and delivering proton treatment beams are discussed along with examples of the implementation of these methods at treatment facilities around the world. Finally, the clinical dosimetry of proton beams is summarized and sample data are presented.

Biophysics↗

PubMed1995

Calorimetric determination of the absorbed dose-to-water beam quality correction factor kQ for high-energy photon beams.

A method has been developed for measuring photon beam quality correction factors kQ using direct transfer with a water calorimeter. kQ values were measured for beam qualities varying between 6 and 23 MV for a Capintec PR-06 and a PTW W30001 cylindrical ionization chamber. Measured values were intercompared with published sets of computed kQ values and agreement was found to be within measurement uncertainty (1%, one standard deviation).

Biophysical Phenomena↗

PubMed1995

Adenoviral-mediated gene transfer to fetal pulmonary epithelia in vitro and in vivo.

Vector-mediated gene transfer offers a direct method of correcting genetic pulmonary diseases and might also be used to correct temporary abnormalities associated with acquired, nongenetic disorders. Because the fetus or newborn may be a more immune tolerant host for gene transfer using viral vectors, we used replication defective recombinant adenoviral vectors to test the feasibility of gene transfer to the fetal pulmonary epithelium in vitro and in vivo. Both proximal and distal epithelial cells in cultured fetal lung tissues from rodents and humans diffusely expressed the lacZ transgene 3 d after viral infection. In vivo gene delivery experiments were performed in fetal mice and lambs. Delivery of Ad2/CMV-beta Gal to the amniotic fluid in mice produced intense transgene expression in the fetal epidermis and amniotic membranes, some gastrointestinal expression, but no significant airway epithelial expression. When we introduced the adenoviral vector directly into the trachea of fetal lambs, the lacZ gene was expressed in the tracheal, bronchial, and distal pulmonary epithelial cells 3 d after viral infection. Unexpectedly, reactive hyperplasia and squamous metaplasia were noted in epithelia expressing lacZ in the trachea, but not in the distal lung of fetal lambs. 1 wk after infection, adenovirus-treated fetuses developed inflammatory cell infiltrates in the lung tissue with CD4, CD8, IgM, and granulocyte/macrophage positive immune effector cells. Transgene expression faded coincident with inflammation and serologic evidence of antiadenoviral antibody production. While these studies document the feasibility of viral-mediated gene transfer in the prenatal lung, they indicate that immunologic responses to E1-deleted recombinant adenoviruses limit the duration of transgene expression.

Adenoviruses, Human↗

PubMed1995

The role of intracerebral insulin in the effect of nutrition on gonadotrophin secretion in mature male sheep.

The effect of nutrition on gonadotrophin secretion may be exerted through a central metabolic signal that reflects nutritional status. We have previously found that glucose and insulin concentrations are elevated in the cerebrospinal fluid (CSF) of rams in which the secretion of gonadotrophins has been stimulated by a nutritional supplement of lupin grain (Lupinus angustifolius). In the present study, we tested the hypothesis that insulin and/or glucose is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion. Six mature rams were fed a diet that maintained live weight and then given a series of infusions, each for 12 h/day for 4 days, in a cross-over design. The treatments were: artificial CSF (aCSF), glucose (50 mumol/h) in aCSF, insulin (0.6 ng/h) in aCSF, and glucose (50 mumol/h) plus insulin (0.6 ng/h) in aCSF; all infused at a rate of 5 microliters/min. At the same time as the infusion treatments, two other groups of four rams without cerebral cannulae were fed either the maintenance diet or the same diet supplemented with 750 g lupin grain per head per day for 4 days, again in a cross-over design. Rams fed the lupin supplement showed an increase in both LH pulse frequency and mean FSH on day 4 (P < 0.05). Infusion of aCSF or glucose did not affect gonadotrophin secretion. Rams infused with insulin or insulin plus glucose showed an increase (P < 0.05) in LH pulse frequency but no increase in FSH concentrations on day 4 of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1994

20 hot job tracks.

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Data Collection↗