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Biomedical subjects

D E Nelson

Publications and source records attributed to D E Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Integration and saturation within the circadian photic entrainment pathway of hamsters.

The sensitivity of the visual pathway that subserves circadian entrainment was measured in hamsters after prior stimulation and using trains of multiple pulses. Immediately after subsaturating stimulation in the late subjective night, there was a significant decrease in responsiveness that persisted for at least 1 h. The reduced responsiveness was not due to light adaptation (shifting of the stimulus-response curve) but rather to response saturation, which appeared to reduce the sensitivity to subsequent stimulation and limit the maximum response of the pacemaker. The system, therefore, integrates the total number of photons delivered in two light stimuli separated in time by up to 1 h. The responsiveness was also measured using stimulus trains containing 10-1,000 individual pulses of equal irradiance and equal total photons. Results suggest that this pathway is responsive to the total photons delivered in all of the stimuli and is not responsive to light onsets or offsets associated with individual stimuli. These data outline several fundamental characteristics of phase shifting for the circadian photic entrainment pathway in hamsters. Knowledge of these characteristics is important for designing and interpreting results of future studies to dissect the cellular and molecular nature of the mammalian circadian clock and for understanding how visual information affects the cellular clock during entrainment.

Adaptation, Ocular↗
PubMed1999

Trends in perceived cost as a barrier to medical care, 1991-1996.

OBJECTIVES: This study examined trends in perceived cost as a barrier to medical care. METHODS: The Behavioral Risk Factor Surveillance System was used to analyze monthly telephone survey data from 45 states. RESULTS: Overall, the percentage of persons perceiving cost as a barrier to medical care increased from 1991 until early 1993 and then declined to baseline values in late 1996. Perceived cost was a greater barrier in 1996 than in 1991 for persons with low incomes and for those who were unemployed and uninsured. For self-employed persons, percentages increased until mid-1993 and then remained constant. CONCLUSIONS: Further efforts are needed to improve access to medical care for socially disadvantaged populations.

Adult↗
PubMed1999

Assessment of health risk behaviors. A tool to inform consumers, providers, health care organizations, and purchasers.

INTRODUCTION: Tobacco use, diet and physical activity patterns, and alcohol use are the leading causes of death in the United States. To make major improvements in the health status of the population, behavioral risk factors for disease must be addressed. METHODS: We propose a brief survey of behavioral risk factors for enrollees of health care organizations, employer groups, or other adult populations that can be used to profile the health risk behaviors of a population, assess performance of prevention and risk reduction programs, or make comparisons with other populations. The survey contains questions about tobacco, diet, physical activity, alcohol, firearms, motor vehicle safety, sexual behavior, and drugs. RESULTS: Recommendations for survey items, implementation, and calculation of performance measures are given. CONCLUSIONS: Widespread adoption of this type of survey would be a major step forward in acknowledging the impact that behavior has on health and in furthering individual and organizational accountability for improving health risk behaviors.

Adult↗
PubMed1998

Regulation of cell-specific inositol metabolism and transport in plant salinity tolerance.

myo-Inositol and its derivatives are commonly studied with respect to cell signaling and membrane biogenesis, but they also participate in responses to salinity in animals and plants. In this study, we focused on L-myo-inositol 1-phosphate synthase (INPS), which commits carbon to de novo synthesis, and myo-inositol O-methyltransferase (IMT), which uses myo-inositol for stress-induced accumulation of a methylinositol, D-ononitol. The Imt and Inps promoters are transcriptionally controlled. We determined that the transcription rates, transcript levels, and protein abundance are correlated. During normal growth, INPS is present in all cells, but IMT is repressed. After salinity stress, the amount of INPS was enhanced in leaves but repressed in roots. IMT was induced in all cell types. The absence of myo-inositol synthesis in roots is compensated by inositol/ononitol transport in the phloem. The mobilization of photosynthate through myo-inositol translocation links root metabolism to photosynthesis. Our model integrates the transcriptional control of a specialized metabolic pathway with physiological reactions in different tissues. The tissue-specific differential regulation of INPS, which leads to a gradient of myo-inositol synthesis, supports root growth and sodium uptake. By inducing expression of IMT and increasing myo-inositol synthesis, metabolic end products accumulate, facilitating sodium sequestration and protecting photosynthesis.

Acclimatization↗
PubMed1998

Trends in safety belt use by demographics and by type of state safety belt law, 1987 through 1993.

OBJECTIVES: This study examined trends in safety belt use by age, sex, race/ethnicity, education, and type of safety belt law. METHODS: We analyzed Behavioral Risk Factor Surveillance System data on safety belt use from 33 states for 1987 through 1993 and used linear regression models to determine trends in prevalence. RESULTS: Asian/Pacific Islanders and Hispanics had the highest safety belt use among racial/ethnic groups. Prevalence varied little from age 25 through 64 years in all years, but averaged 25 percentage points higher in states with primary laws than in states with no belt laws. Overall safety belt use increased by an average 2.7 +/- 0.1 percentage points per year and varied little across most demographic groups, but there was no significant increase for Black males aged 18 through 29 years. CONCLUSIONS: The generally consistent increased in safety belt use across demographic groups is in sharp contrast to trends in other health-risk behaviors. States should enact primary safety belt laws and focus safety belt use efforts towards young Black males.

Adult↗
PubMed1998

State estimates of household exposure to firearms, loaded firearms, and handguns, 1991 through 1995.

OBJECTIVES: Variations among states in household exposure to firearms, loaded firearms, and handguns were examined. METHODS: Data from the Behavioral Risk Factor Surveillance System in 22 states were used to estimate the prevalence of adults and children exposed to household firearms. RESULTS: The prevalence of adults living in households with firearms ranged from 12% to 57%; the corresponding ranges were 1% to 23% for loaded firearms and 5% to 36% for handguns. The prevalence of children less than 18 years of age living in households with loaded firearms ranged from 2% to 12%. CONCLUSIONS: Important variations among states exist in the prevalence of adults and children living in households with firearms, loaded firearms, and handguns.

Adolescent↗
PubMed1998

Telephone coverage and measurement of health risk indicators: data from the National Health Interview Survey.

OBJECTIVES: This study compared health behavior variables for all US households and households with telephones to measure the potential impact of telephone coverage on estimates from telephone surveys. METHODS: Data were derived from the 1991 through 1994 version of the National Health Interview Survey. RESULTS: Ninety-five percent of respondents lived in households with telephones. Differences in health indicators were small (< 1%) in comparisons between all households and those with telephones. Results were similar when only respondents below the poverty level were included. CONCLUSIONS: Telephone noncoverage effects appear to be small, supporting the use of telephone surveys for health risk behavior surveillance with most population groups.

Adult↗
PubMed1997

Patterns of health risk behaviors for chronic disease: a comparison between adolescent and adult American Indians living on or near reservations in Montana.

PURPOSE: To compare the chronic disease health risk behavior patterns of adolescents and adults among American Indians living on or near reservations in Montana. METHODS: We analyzed data from the 1993 Youth Risk Behavior Survey of American Indians in Grades 9-12 living on or near Montana reservations. Risk factors included tobacco use, low physical activity, attempted weight loss, and low consumption of fruits, vegetables, and green salad. Similar data were analyzed from a 1994 Behavioral Risk Factor Survey of American Indian adults living on or near reservations in Montana. RESULTS: The prevalence of most adolescent health risk behaviors was high, especially cigarette smoking (45% for males, 57% for females), smokeless tobacco use (44% for males, 30% for females), and infrequent consumption of salad or vegetables (59-76%). With the exception of daily cigarette smoking and inadequate fruit consumption among adolescents of both genders and physical inactivity among adolescent males, the prevalence of chronic disease health risk behaviors among adolescents was similar to or higher than the prevalence of the same risk behaviors among adults. CONCLUSIONS: Many health risk behaviors for chronic diseases are common by the time this group of American Indians in Montana has reached adolescence. Possible reasons may include modeling of familial behaviors, peer pressure, advertising, or age cohort effects. If these risk behavior patterns continue into adulthood, morbidity and mortality from chronic diseases are likely to remain high. Substantial efforts are needed to prevent or reduce health risk behaviors among adolescents and adults in this population.

Adolescent↗
PubMed1997

Induction of a ribosome-inactivating protein upon environmental stress.

Transcripts of altered abundance in RNA from unstressed and 500 mm salt-shocked Mesembryanthemum crystallinum (common ice plant) were detected by reverse-transcription differential display (RT-DD). One transcript, Rip1, was of very low abundance in unstressed plants and was strongly induced by stress. RNA blot hybridizations showed strong induction and a diurnal rhythm of transcript abundance with a maximum each day around the middle of the light phase. Rip1 encodes a reading frame of 289 amino acids (molecular mass 32,652), RIP1, with homology to single-chain ribosome inactivating proteins (rRNA N-glycosidases). The deduced amino acid sequence is 31.7% identical to pokeweed antiviral protein RIP-C (overall similarity 66.5%) with highest identity in domains of documented functional importance. RT-DD also detected mRNA for pyruvate, orthophosphate dikinase (PPDK) which has already been shown to be stress-induced in the ice plant [16]. RIP1, expressed in Escherichia coli, showed rRNA N-glycosidase activity against ice plant and rabbit reticulocyte ribosomes. The induction of Rip1 coincides with the transition period during which global changes in translation lead to adaptation of the ice plant to salt stress.

Amino Acid Sequence↗
PubMed1997

The expression of an aquaporin promoter from Mesembryanthemum crystallinum in tobacco.

The promoter region of the MipB gene encoding an aquaporin from Mesembryanthemum crystallinum was isolated and used in a transcriptional fusion to control uidA expression in tobacco. The sequence of the promoter was determined for 2 kb upstream of the translation initiation site. Three start sites were utilized with approximately equal frequency, located 176, 170, and 161 bases, respectively, upstream of the translation initiation site. As judged by analysis of GUS expression, promoter MipB retains its specificity in transgenic tobacco. In germinating seedlings, all cells showed GUS expression of different intensities with the strongest signals in root meristems. In older seedlings, GUS staining was observed in rapidly expanding cells--root and apical meristem, and lateral root primordia. In mature plants, strong GUS activity was located to glandular trichomes, subepidermal cells of the stem and petioles, to cells surrounding vascular tissues as well as in xylem parenchyma cells. In immature floral organs, GUS expression was strong in sepals, petals, stamen, and pistil. The intensity declined as they matured. In general, this promoter was active in rapidly expanding cells and cells with high water flux capacity, especially in the xylem parenchyma.

Aquaporins↗
PubMed1997

Abundant accumulation of the calcium-binding molecular chaperone calreticulin in specific floral tissues of Arabidopsis thaliana.

Calreticulin (CRT) is a calcium-binding protein in the endoplasmic reticulum (ER) with an established role as a molecular chaper-one. An additional function in signal transduction, specifically in calcium distribution, is suggested but not proven. We have analyzed the expression pattern of Arabidopsis thaliana CRTs for a comparison with these proposed roles. Three CRT genes were expressed, with identities of the encoded proteins ranging from 54 to 86%. Protein motifs with established functions found in CRTs of other species were conserved. CRT was found in all of the cells in low amounts, whereas three distinct floral tissues showed abundant expression: secreting nectaries, ovules early in development, and a set of subepidermal cells near the abaxial surface of the anther. Localization in the developing endosperm, which is characterized by high protein synthesis rates, can be reconciled with a specific chaperone function. Equally, nectar production and secretion, a developmental stage marked by abundant ER, may require abundant CRT to accommodate the traffic of secretory proteins through the ER. Localization of CRT in the anthers, which are degenerating at the time of maximum expression of CRT, cannot easily be reconciled with a chaperone function but may indicate a role for CRT in anther maturation or dehiscence.

Arabidopsis↗
PubMed1997

Photoperiodic time measurement in tau mutant hamsters.

Photoperiodic regulation of testicular function was investigated in homozygous tau mutant hamsters; these animals have an innate circadian period of about 20 h. In 20-h light:dark (LD) cycles, the minimum photoperiod required to prevent testicular regression was between 10.0 and 11.5 h per 20-h cycle (equivalent to 12.0-13.8 circadian hours). This was proportionally similar to the minimum photoperiod necessary to prevent regression in wild-type hamsters maintained in 24-h LD cycles. To examine the shape of the photoperiodic photosensitivity curve in homozygous tau mutant hamsters, the authors measured the effects of different T cycles on testicular maintenance. Entrainment to LD 1:18.0 and LD 1:20.5 partially or completely prevented gonadal regression in homozygous tau mutant hamsters, but LD 1:19.4 did not prevent regression. When considered in terms of circadian time, the photoperiodic photosensitivity curve for homozygous tau mutant hamsters was similar to that described previously for wild-type hamsters. The results indicate that, as in wild-type hamsters, photoperiodic regulation of reproduction is regulated by circadian photosensitivity in homozygous tau mutant hamsters. Because tau mutant hamsters measure day length against a time base of 20 h, the circadian pacemaker that measures day length might be the same as that which generates circadian rhythmicity in locomotor activity. The authors' data leave open the question of whether the tau mutation has had effects on the control of reproduction that are not directly attributable to its effects on the period of the circadian oscillator.

Animals↗
PubMed1997

State smoking prevalence estimates: a comparison of the Behavioral Risk Factor Surveillance System and current population surveys.

OBJECTIVES: This study examined whether there are systematic differences between the Behavioral Risk Factor Surveillance System (BRFSS) and the Current Population Survey (CPS) for state cigarette smoking prevalence estimates. METHODS: BRFSS telephone survey estimates were compared with estimates from the US Census CPS tobacco-use supplements (the CPS sample frame includes persons in households without telephones). Weighted overall and sex- and race-specific BRFSS and CPS state estimates of adults smoking were analyzed for 1985, 1989, and 1992/1993. RESULTS: Overall estimates of smoking prevalence from the BRFSS were slightly lower than estimates from CPS (median difference: -2.0 percentage points in 1985, -0.7 in 1989, and -1.9 in 1992/1993; P < .05 for all comparisons), but there was variation among states. Differences between BRFSS and CPS estimates were larger among men than among women and larger among Blacks than among Hispanics or Whites; for most states, these differences were not significant. CONCLUSIONS: The BRFSS generally provides state estimates of smoking prevalence similar to those obtained from CPS, and these are appropriate for ongoing state surveillance of smoking prevalence.

Adult↗
PubMed1996

Population estimates of household firearm storage practices and firearm carrying in Oregon.

OBJECTIVES: To examine statewide data on exposure of adults and children to loaded and unlocked household firearms, and to estimate the prevalence of firearm carrying among adults in Oregon. DESIGN: Analyses of 1992 and 1993 telephone survey data from 6202 adults aged 18 years and older using the Oregon Behavioral Risk Factor Surveillance System. MAIN OUTCOME MEASURES: Number of adults and children exposed to household firearms always or sometimes stored loaded and unlocked. Adjusted odds ratios (ORs) for exposure to loaded and unlocked firearms and firearm carrying among adults by demographic and alcohol use patterns. RESULTS: Ten percent of adults (197 400 persons) lived in households with firearms that were always or sometimes stored loaded and unlocked. An estimated 6.2% of households with children had firearms that were loaded and unlocked, and about 40 000 children lived in these households. Overall, 4.4% of adults carried loaded firearms in the past month. Rural residence, male sex, and less than a college education were associated with living in a household with loaded and unlocked firearms and with firearm carrying. Drinking 5 or more alcoholic beverages on 1 or more occasions in the past month (OR, 1.7; 95% confidence interval, 1.3-2.3) or drinking 60 or more alcoholic beverages in the past month (OR, 1.8; 95% confidence interval, 1.2-2.7) were independently associated with living in households with loaded and unlocked firearms. CONCLUSIONS: Many adults and children are exposed to unsafely stored firearms in Oregon, and many adults carry loaded firearms. Improved public health surveillance of firearm storage and firearm carrying using standardized questions and definitions is needed at the national, state, and local levels.

Adolescent↗
PubMed1996

Validity of self reported data on injury prevention behavior: lessons from observational and self reported surveys of safety belt use in the US.

OBJECTIVES: To examine the validity of self reported data on safety belt use and to consider the implications for research on injury prevention behaviors. METHODS: 1992 and 1993 self reported data on safety belt use were obtained from the Behavioral Risk Factor Surveillance System and observational data were obtained from the National Highway Traffic Safety Administrations for 49 states in 1992 and 50 states in 1993. The ratio of self reported to observed belt use was calculated for each state, and linear regression models were used to examine the association between the two methods. RESULTS: There was variation between states, but the overall median ratio of self reported to observed safety belt use was 1.05 in 1992 (interdecile range 0.87-1.36) and 1.02 in 1993 (interdecile range 0.87-1.31). Self reports were substantially higher in southern states and in states with the lowest levels of observed use. Linear regression models indicated a moderately strong association between state estimates using both methods. For every percentage point increase in self reported data in 1993, observed safety belt use increased by 0.95 percentage point. CONCLUSIONS: In the aggregate, self reported estimates were only 2% to 5% higher than observed estimates. This is a substantial improvement from previous studies. This is probably due to the increased prevalence of safety belt use and the declining effects of social desirability on self reported use. In general, the validity of self reported estimates of socially desirable injury prevention behaviors will be higher when the actual prevalence of the behavior is higher, but lower when this is not true.

Accident Prevention↗
PubMed1996

Trends in smokeless tobacco use among men in four states, 1988 through 1993.

OBJECTIVES: Trends in smokeless tobacco use were examined for men in Indiana, Iowa, Montana, and West Virginia from 1988 through 1993. METHODS: State survey data from the Behavioral Risk Factor Surveillance System (BRFSS) were analyzed. RESULTS: Demographic characteristics associated with smokeless tobacco use included age less than 35 years, a high school education or less, and rural residence. Overall, there was little change in smokeless tobacco use among men in these states (range = -0.4-0.4 percentage points annually); only West Virginia had a significant decline. CONCLUSIONS: Reasons for the overall lack of decline may include increased advertising and promotional expenditures or substitution of smokeless tobacco for cigarettes. Increased prevention and cessation efforts are needed.

Adolescent↗