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Biomedical subjects

J C Miller

Publications and source records attributed to J C Miller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Design and synthesis of enantiomers of 3,5-dinitro-o-tyrosine: alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA) receptor antagonists.

The R- and S-isomers of 3,5-dinitro-o-tyrosine (6a,b) have been synthesized through the use of chemoenzymatic synthesis and shown to bind differentially with the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid (AMPA, 3) receptors. The phenolic functional group of these o-tyrosine analogues was designed to act as a bioisostere of the gamma-carboxyl group of glutamate. The S-isomer of 3,5-dinitro-o-tyrosine (6b) was 6.5 times more potent than the R-isomer (6a) in inhibiting [3H]AMPA binding with IC50 values of 13 +/- 7 and 84 +/- 26 microM, respectively. The phenolic group was important for binding affinity since the methoxy compound 7 was less potent than the phenolic compound 6 in inhibiting the binding of AMPA. The free amino group was also shown to be important since the N-acetyl analogue 15 and the N-t-BOC compounds 16 and 17 exhibited very low affinity for the AMPA receptors. AMPA receptor functional tests showed that the o-tyrosine analogues are antagonists and that the S-isomer 6b (IC50 = 630 +/- 140 microM) was more potent than the racemate 6 (IC50 = 730 +/- 88 microM) while the R-isomer 6a was inactive up to 1 mM concentration, which is consistent with the S-isomer having higher binding affinity than the R-isomer.

Animals↗
PubMed1998

Flash decaging of tyrosine sidechains in an ion channel.

A nonsense codon suppression technique was employed to incorporate ortho-nitrobenzyl tyrosine, "caged tyrosine," in place of tyrosine at any of three positions (93, 127, or 198) in the alpha subunit of the muscle nicotinic ACh receptor (nAChR) expressed in Xenopus oocytes. The ortho-nitrobenzyl group was then removed by 1 ms flashes at 300-350 nm to yield tyrosine itself while macroscopic currents were recorded during steady ACh exposure. Responses to multiple flashes showed (1) that each flash decages up to 17% of the tyrosines and (2) that two tyrosines must be decaged per receptor for a response. The conductance relaxations showed multiple kinetic components; rate constants (<0.1 s(-1) to 10(3) s(-1)) depended on pH and the site of incorporation, and relative amplitudes depended on the number of prior flashes. This method, which is potentially quite general, (1) provides a time-resolved assay for the behavior of a protein when a mutant sidechain is abruptly changed to the wild-type residue and (2) will also allow for selective decaging of sidechains that are candidates for covalent modification (such as phosphorylation) in specific proteins in intact cells.

Acetylcholine↗
PubMed1998

Growth hormone, fatigue, poor sleep, and disability in HIV infection.

Poor sleep, daytime fatigue, and loss of cognitive ability exist during all stages of HIV infection, worsening with disease progression. These symptoms contribute to disability and poor quality of life. Data from several research groups support a role of somnogenic inflammatory process peptides elevated in HIV infection, e.g. TNF alpha. Though the literature is in conflict regarding an effect of HIV infection on growth hormone (GH) secretion, GH axis dysregulation and treatment with GH may be important in HIV infection, e.g. in the wasting syndrome. It has long been known that GH varies with changes in sleep. The hypothesis tested in the current study was that the relationship between delta frequency (0.5-4.0 Hz) sleep EEG amplitude (square root of power from frequency analysis) and GH secretion would differ between HIV positive (HIV+) and HIV negative (HIV-) subjects. In 14 subjects (6 HIV+ and 8 HIV-, none with current or past AIDS-defining illness) a linear relationship change across the night's sleep was found in the coupling between delta frequency sleep EEG amplitude and GH secretion. The phase coupling change was in opposite directions in HIV+ versus HIV- subjects. This difference supports the hypothesis that the brain-based coordination of sleep and sleep-related physiology deteriorates early in HIV infection, and that GH dysregulation may contribute to this sleep pathology.

Adult↗
PubMed1998

As others see us, Part 2. Goals and the annual report: a system for performance evaluation.

This systematic approach to an annual performance report can show that laboratory professionals are active outside the physical laboratory as a vital part of the healthcare team. The annual report also provides an opportunity to show the many dimensions of clinical laboratory science and presents evidence of the multifaceted role of the laboratory manager. The annual report shows that employees can be self-directed and creative in goal setting and in achieving goals. In addition, the annual report is helpful should a laboratorian decide to apply for a promotion or other position. Also, the annual report documents a track record and demonstrates abilities and qualifications to prospective employers for expanded careers outside the laboratory. But most importantly, the annual report can be used as a road map for insight into professional growth and development.

Annual Reports as Topic↗
PubMed1997

Differential regulation of D2 receptor gene expression by transcription factor AP-1 in cultured cells.

The role of the transcription factor AP-1 in regulating D2 receptor transcriptional activity was investigated in D2 receptor expressing neuroblastoma cells, NB41A3, and in non-D2 receptor expressing CHO cells. Deletion of a region containing the putative AP-1 binding site resulted in a significant reduction in the activity in CHO cells; while the activity in NB41A3 cells was increased suggesting that the AP-1 site may differentially regulate D2 gene expression in these distinct cell types. However, both cell lines were found to express significant and similar levels of the transcription factors AP-1. Analysis of phosphorylated proteins in each of the cell lines provided evidence that AP-1 is phosphorylated in NB41A3 cells, but not in CHO cells. This result suggests that differential regulation of D2 gene expression may be related to AP-1 phosphorylation.

Animals↗
PubMed1997

The sleep of long-haul truck drivers.

BACKGROUND: Fatigue and sleep deprivation are important safety issues for long-haul truck drivers. METHODS: We conducted round-the-clock electrophysiologic and performance monitoring of four groups of 20 male truck drivers who were carrying revenue-producing loads. We compared four driving schedules, two in the United States (five 10-hour trips of day driving beginning about the same time each day or of night driving beginning about 2 hours earlier each day) and two in Canada (four 13-hour trips of late-night-to-morning driving beginning at about the same time each evening or of afternoon-to-night driving beginning 1 hour later each day). RESULTS: Drivers averaged 5.18 hours in bed per. day and 4.78 hours of electrophysiologically verified sleep per day over the five-day study (range, 3.83 hours of sleep for those on the steady 13-hour night schedule to 5.38 hours of sleep for those on the steady 10-hour day schedule). These values compared with a mean (+/-SD) self-reported ideal amount of sleep of 7.1+/-1 hours a day. For 35 drivers (44 percent), naps augmented the sleep obtained by an average of 0.45+/-0.31 hour. No crashes or other vehicle mishaps occurred. Two drivers had undiagnosed sleep apnea, as detected by polysomnography. Two other drivers had one episode each of stage 1 sleep while driving, as detected by electroencephalography. Forty-five drivers (56 percent) had at least 1 six-minute interval of drowsiness while driving, as judged by analysis of video recordings of their faces; 1067 of the 1989 six-minute segments (54 percent) showing drowsy drivers involved just eight drivers. CONCLUSIONS: Long-haul truck drivers in this study obtained less sleep than is required for alertness on the job. The greatest vulnerability to sleep or sleep-like states is in the late night and early morning.

Adult↗
PubMed1997

The effect of different TP53 mutations on the chromosomal stability of a human colonic adenoma derived cell line with endogenous wild type TP53 activity, before and after DNA damage.

We examined the effect of loss of wild type TP53 activity on the chromosomal stability of a human colonic adenoma derived cell line (designated AA/Cl) by studying transfected variants which express different TP53 mutations. Using gross chromosomal aberrations as a measure of instability, we studied metaphase spreads of a vector control cell line (AA/PCMV) and variants expressing the 143(Val-Ala) mutation, which retain endogenous wild type TP53 activity, or the 273(Arg-His) TP53 mutation, which acts as a dominant negative. It was found that the proportion of cells with more than 4% aberrations was significantly greater in the AA/273p53/B cell line (an approximate 5-Fold increase) than in the vector control or the AA/143p53/A cell line. To investigate whether loss of TP53 dependent checkpoints also predisposed the cells to accumulate persistent chromosomal aberrations after DNA damage, cells were exposed to 5 Gy gamma radiation. Regardless of TP53 status, cells with radiation induced chromosomal damage were eliminated through a TP53 independent mechanism, suggesting that loss of TP53 activity did not permit the survival of these cells. In contrast, when exposed to low level gamma radiation (0.2 Gy), decreased wild type TP53 function and/or expression of mutant TP53 protein led to increased radioresistance (both in the non-dominant as well as the dominant mutant expressing cell lines). These findings suggest that loss of TP53 activity and/or acquisition of specific TP53 mutations can increase chromosomal instability and resistance to low level DNA damage in human colonic adenoma cells. This study emphasises the different biological consequences of individual TP53 mutations on the genotype of premalignant colorectal epithelial cells and subsequent implications for tumorigenic progression.

Adenoma↗
PubMed1997

Basal and stimulated C-fos mRNA expression in the rat brain: effect of chronic dietary lithium.

The mechanisms underlying the therapeutic efficacy of lithium in affective disorders are poorly understood; however, previous studies have established an influence of lithium on receptor-coupled and postreceptor signal transduction mechanisms, including the transcription factor c-fos. We investigated the effect of chronic lithium on basal, stress-, muscarinic-, and haloperidol-induced c-fos mRNA expression in various rat brain regions. Chronic lithium produced significant reductions in basal c-fos expression in the frontal cortex and hippocampus, confirming our previous report. Stress-induced c-fos was significantly attenuated in the frontal cortex, hippocampus, and pituitary, was increased in the occipital cortex, and unchanged in the hypothalamus by chronic lithium. Pilocarpine-induced c-fos was significantly reduced in the frontal cortex and hippocampus by chronic lithium, but was enhanced in the occipital cortex and hypothalamus. Haloperidol-induced c-fos was augmented in the striatum and pituitary, but reduced in the frontal cortex by chronic lithium treatment. In regions in which haloperidol did not induce fos expression in control animals, fos levels after haloperidol were reduced after chronic lithium. One week after discontinuation of the lithium treatment, basal c-fos levels remained significantly lower in the frontal cortex and hippocampus, whereas the effects of stress, pilocarpine, or haloperidol on fos were normalized in most regions, except in the hippocampus, where the attenuated fos response to injection stress persisted. We suggest that repression of basal fos expression and inhibition and activation of inducible fos may be factors to be considered in the longer-term effects of lithium, leading to changes in expression of genes that regulate fos and are regulated by Fos, and ultimately to alterations in the functional activity of neural systems involved in the pathophysiology of affective disorder.

Amino Acid Isomerases↗
PubMed1997

An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods.

The aim of this study was to systematically compare postprandial insulin responses to isoenergetic 1000-kJ (240-kcal) portions of several common foods. Correlations with nutrient content were determined. Thirty-eight foods separated into six food categories (fruit, bakery products, snacks, carbohydrate-rich foods, protein-rich foods, and breakfast cereals) were fed to groups of 11-13 healthy subjects. Finger-prick blood samples were obtained every 15 min over 120 min. An insulin score was calculated from the area under the insulin response curve for each food with use of white bread as the reference food (score = 100%). Significant differences in insulin score were found both within and among the food categories and also among foods containing a similar amount of carbohydrate. Overall, glucose and insulin scores were highly correlated (r = 0.70, P < 0.001, n = 38). However, protein-rich foods and bakery products (rich in fat and refined carbohydrate) elicited insulin responses that were disproportionately higher than their glycemic responses. Total carbohydrate (r = 0.39, P < 0.05, n = 36) and sugar (r = 0.36, P < 0.05, n = 36) contents were positively related to the mean insulin scores, whereas fat (r = -0.27, NS, n = 36) and protein (r = -0.24, NS, n = 38) contents were negatively related. Consideration of insulin scores may be relevant to the dietary management and pathogenesis of non-insulin-dependent diabetes mellitus and hyperlipidemia and may help increase the accuracy of estimating preprandial insulin requirements.

Adult↗
PubMed1997

Easy gene walking.

Explore the source record for details and available documents.

Chromosome Walking↗
PubMed1997

Quantitative analysis of truck driver EEG during highway operations.

Scalp electroencephalograms (EEGs) were collected from each of 80 male, commercial truck drivers during one week of open-highway driving (4 or 5 round trips per week; about 50 hours of driving per driver) as part of the Driver Fatigue and Alertness Study funded by the Federal Highway Administration. Features of the central EEG were selected for extraction based upon known characteristics of the EEG spectrum during sleep onset. Data reduction focused on the contributions to total EEG power from the theta, alpha, sigma and beta spectral bands. The means and regression slopes for the EEG measures were calculated on the time axis and used to estimate EEG values at the beginning and end of each leg of each trip for each driver. The weekly patterns of EEG power appeared to be interpretable by reference to expected circasemidian rhythms. The EEG sigma/beta ratio may provide an index of midafternoon sleepiness while driving.

Adult↗
PubMed1996

Electrooculographic and performance indices of fatigue during simulated flight.

The investigation evaluated specific components of eye and eyelid movement as predictors of performance decrements resulting from pilot fatigue. Ten partially sleep deprived pilots flew a GAT-1 moving-base flight simulator on a 4.5-h sortie. The scored flight portion consisted of eight legs, each leg made up of two segments, a flight maneuvers task (FMT) and a straight and level flying task (SLT). Error scores were calculated across altitude, airspeed, heading, and vertical velocity. An electrooculogram provided measures of blink rate (BR), blink duration, long closure rate (LCR), blink amplitude (BA), saccade velocity, saccade rate, and peak saccade velocity. Subjective fatigue, workload and sleepiness were estimated using the USAFSAM seven-point forced-choice scales, the Stanford Sleepiness Scale, and the USAFSAM Sleep Survey Form. Error scores increased significantly during the first seven legs of the sortie and decreased slightly for the last leg. Subjective reports of fatigue increased significantly over time and were positively correlated with increased error. For the combined data set and for FMTs alone, BA was the best predictor of changes in error with decreased amplitude corresponding to increased error. BR and LCR were the second and third best predictors, respectively. For SLTs alone, LCR and BA were the first and second best predictors of increased error, respectively. The investigation demonstrated that measurable flying performance decrements do occur due to changes in fatigue and that one can measure physiological correlates of those performance decrements.

Adult↗
PubMed1996

Interleukin-1 beta induces prostaglandin G/H synthase-2 (cyclooxygenase-2) in primary murine astrocyte cultures.

Activation of glial cells and the consequent release of cytokines, proteins, and other intercellular signaling molecules is a well-recognized phenomenon in brain injury and neurodegenerative disease. We and others have previously described an inducible prostaglandin G/H synthase, known as PGHS-2 or cyclooxygenase-2, that is up-regulated in many cell systems by cytokines and growth factors and down-regulated by glucocorticoid hormones. In cultured mouse astrocytes we observed increased production of prostaglandin E2 (PGE2) after stimulation with either interleukin-1 beta (IL-1 beta) or the protein kinase C activator phorbol 12-myristate 13-acetate (TPA). This increase in PGE2 content was blocked by pretreatment with dexamethasone and correlated with increases in cyclooxygenase activity measured at 4 h. Northern blots revealed concomitant increases in PGHS-2 mRNA levels that peaked at 2 h and were dependent on the dosage of IL-1 beta. Dexamethasone inhibited this induction of PGHS-2 mRNA by IL-1 beta. TPA, basic fibroblast growth factor, and the proinflammatory factors tumor necrosis factor alpha and lipopolysaccharide, but not interleukin-6, also stimulated PGHS-2 mRNA expression. Relative to IL-1 beta, the greater increases in PGE2 production and cyclooxygenase activity caused by TPA correlated with a greater induction of PGHS-2 mRNA. Furthermore NS-398, a specific inhibitor of cyclooxygenase-2, blocked > 80% of the cyclooxygenase activity in TPA-treated astrocytes. These findings indicate that increased expression of PGHS-2 contributes to prostaglandin production in cultured astrocytes exposed to cytokines and other factors.

Animals↗
PubMed1996

Methods of testing for sleepiness [corrected].

Normal nonrandom fluctuation in daily human performance have been documented for years. Published research reports have shown patterns of workers' errors in reading gas meters, operators' delays in answering calls, drivers' drowsiness, sleepy locomotive engineers' automatic breaking, vehicle crashes, deaths resulting from disease, brief periods of sleep, and sleep latency in structured naps. The authors summarized these data sets and fitted them with a two-peak-per-day cosine curve derived from the population growth function used in chaos theory. Median parameters extracted from the curve fits predicted a sharp peak of sleepiness at 2:30 AM and a secondary peak at 2:30 PM. The shape of the curve was modified by a nonlinear sleep-deprivation factor. The model appeared to be biological rather than behavioral or social because it applied well to disease-related deaths. The authors also review measurement of sleepiness through electroencephalographic monitoring, self-reports, pupillography, and the Multiple Sleep Latency and the Maintenance of Wakefulness Tests.

Circadian Rhythm↗
PubMed1996

Amylopectin starch induces nonreversible insulin resistance in rats.

Starches that are high in amylopectin are digested and absorbed more quickly than starches with a high amylose content and produce insulin resistance in rats during long-term feeding. The aim of this study was to determine whether amylopectin-induced insulin resistance could be prevented or reversed by a period of high amylose feeding. We employed a randomized design in which two groups of rats were fed either the high amylose and then the high amylopectin diet for two consecutive 8-wk periods or vice versa (high amylopectin and then high amylose). Four other groups were fed either a high amylose or a high amylopectin diet for 8 or 16 wk. All rats were fed two 10-g meals per day (300 kJ/d), and insulin sensitivity was assessed by intravenous glucose tolerance test (IVGTT) after 8 or 16 wk of feeding. We found no difference in glucose tolerance between any group at any time point. Insulin responses, however, were 50% higher (P < 0.01) after 16 wk of high amylopectin feeding [area under the plasma insulin curve (AUC) = 18.1 +/- 1.4 nmol.L-1 x 15 min] compared with high amylose feeding (AUC = 13.0 +/- 1.2 nmol.L-1 x 15 min). The two groups which received both diets developed a similar degree of insulin resistance, equivalent to that after 16 wk of high amylopectin feeding. The findings suggest that amylopectin-induced insulin resistance cannot be reversed or prevented by either a subsequent or previous period of amylose feeding. Taken together, the data suggest that the nature of starch in the Western diet influences the development of noninsulin-dependent diabetes mellitus in humans.

Amylopectin↗
PubMed1996

Functional identification of genes up- and down-regulated by glucocorticoids in AtT-20 pituitary cells using an enhancer trap.

The AtT-20/D1 mouse pituitary tumor cell line has been used to study glucocorticoid regulation of POMC. We have used an enhancer trap to determine whether other glucocorticoid-regulated genes exist in AtT-20 cells. An enhancer trap is a recombinant construction containing a selectable marker driven by a promoter that has been weakened by removal of its enhancers so that the transfected trap is only expressed if it comes under the influence of an endogenous enhancer. For a selectable marker, we used a fusion gene coding for hygromycin phosphotransferase (Hy) and herpes simplex thymidine kinase. Thus, expression of this gene conferred hygromycin resistance and ganciclovir sensitivity. Suppression resulted in ganciclovir resistance and hygromycin sensitivity. An enhancerless promoter was produced using a truncated, transcriptionally inactive, form of the POMC promoter. AtT-20/D1 cells were transfected with this construct and cultured in medium containing hygromycin to kill any cells not expressing the Hy gene. The survivors were cultured in medium containing ganciclovir and dexamethasone and cloned. Clones in which the transgene was down-regulated by dexamethasone survived and were designated AtT-20/NET (for negative enhancer trap). Northern blot analysis confirmed that the transgene was down-regulated by dexamethasone as expected and that in at least one instance, suppression of the transgene was more complete than suppression of the full-length POMC promoter. Southern blot analysis after restriction enzyme digestion showed that each cell clone contained a single copy of the transgene, and PCR analysis of the promoter region showed that insertion had occurred in two unique sites in at least two cell clones. Another plasmid construct was prepared that contained the selectable gene but lacked any promoter elements. After transfection of AtT-20 cells with this vector, up-regulated enhancers were trapped by selection in hygromycin and dexamethasone followed by ganciclovir alone and designated AtT-20/PET cells (for positive enhancer trap). Up-regulation of the selectable gene in AtT-20/PET cells was confirmed by Northern blot analysis of dexamethasone-treated cells. In summary, glucocorticoid-regulated enhancers have been identified in AtT-20/D1 cells by an enhancer trap strategy that uses sequential selection under conditions that test whether the transgene is active. These results indicate that in addition to the well characterized, down-regulated POMC gene, there are other glucocorticoid-regulated genes in AtT-20/D1 cells that are both up-regulated and down-regulated by glucocorticoids.

Animals↗
PubMed1996

The role of managed care in work-related injuries.

Many opportunities exist today for orthopedic surgeons in the treatment and management of work-related injuries. Physicians wishing to enter or participate in this market must realize that the role of the physician in the treatment of the injured worker has expanded from one of being solely the care giver to being a patient manager, a problem solver, and a communicator. A number of years ago, many orthopedic surgeons missed out on managed care contracting for health maintenance organizations because they thought they could survive without it. They soon learned the challenges of sitting on the sidelines. Whether we like it or not, managed care for work-related injuries is here and its likelihood for going away is about zero. If your state has not yet adopted utilization management standards or managed care for workers' compensation-enabling legislation, when you wake up tomorrow they may have done so. Because of its relative embryonic development, there are exceptional opportunities for practitioners to take active roles in shaping the models that will serve employees and employers in the year 2000. Physicians who are interested in the treatment of injured workers have a unique opportunity right now to develop relationships in the managed workers' compensation arena. Payment and patient referrals for workers' compensation may turn out to be more attractive financially than many of the contracts currently in place with health maintenance organizations and other general health plans. Physicians willing to partner with employers and other players in the workers' compensation arena currently face some challenging, rewarding, and exciting opportunities. In the immortal words of Hippocrates, "Healing is a matter of time, but it is sometimes a matter of opportunity."3 It is unclear whether Hippocrates ever imagined our current level of science, practice, and organization, but it is clear the opportunities to be an active participant in the changes occurring in workers' compensation are as real today as they were in 1973 when then President Nixon passed the Health Maintenance Organization Act.

Accidents, Occupational↗