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Biomedical subjects

D E Nelson

Publications and source records attributed to D E Nelson.

At least 73 records · Page 4Linked to original sources

Smoking policies of licensed child day-care centers in the United States.

The authors analyzed data from a national survey of 2003 directors of licensed child day-care centers to determine employee smoking policies, measure compliance with state and local employee smoking regulations for child day-care centers and state clean indoor air laws, and to estimate the extent of exposure to environmental tobacco smoke in these settings. Forty states regulated employee smoking in child day-care centers, but only three states required day-care centers to be smoke-free indoors. More than 99% of licensed child day-care centers had employee smoking policies that complied with the appropriate state or local smoking regulations. Nearly 55% of centers were smoke-free indoors and outdoors, and 26% were smoke-free indoors only. The best predictors of more stringent employee smoking policies were location in the West or South, smaller size, independent ownership, or having written smoking policies. Despite the presence of strong smoking policies at the majority of licensed child day-care centers, more than 752,000 children in the United States are at risk for environmental tobacco smoke exposure in these settings. Health care professionals and parents should insist that child day-care centers be smoke-free indoors and, preferably, smoke-free indoors and outdoors.

Centers for Disease Control and Prevention, U.S.↗

The 1990 Montana initiative to increase cigarette taxes: lessons for other states and localities.

In November 1990, voters in Montana defeated an initiative that would have increased the state's excise tax on a pack of cigarettes by 25 cents. The increased revenues were intended for tobacco education and research. Opponents of the measure, primarily tobacco companies, outspent proponents by more than 35 to 1. Their primary themes were opposition to new taxes and to a larger state bureaucracy. Based on the results of initiative campaigns in Montana and California, taxation initiatives are more likely to succeed if guidance is sought from leaders of similar campaigns in other states, tobacco control coalitions are built and funding secured early, and polling conducted before initiative measures are finalized. Other requirements for success include careful wording of the initiative, strong leadership, consideration of a paid petition drive, effective use of the news media, anticipating opposition arguments, and emphasizing the benefits of the tax increase in the campaign.

Adolescent↗

Regulation of jun-B messenger RNA and AP-1 activity by light and a circadian clock.

The suprachiasmatic nuclei (SCN) of the hypothalamus comprise the primary pacemaker responsible for generation of circadian rhythms in mammals. Light stimuli that synchronize this circadian clock induce expression of the c-fos gene in rodent SCN, which suggests a possible role for Fos in circadian entrainment. Appropriate light stimuli also induce the expression of jun-B messenger RNA in the SCN of golden hamsters but only slightly elevate c-jun messenger RNA levels. In addition, light increases the amount of a protein complex in the SCN that binds specifically to sites on DNA known to mediate regulation by the AP-1 transcription factor. The photic regulation of both jun-B messenger RNA expression and AP-1 binding activity is dependent on circadian phase: only light stimuli that shift behavioral rhythms induce jun-B and AP-1 expression. Thus, light and the circadian pacemaker interact to regulate a specific set of immediate-early genes in the SCN that may participate in entrainment of the circadian clock.

Animals↗

Equestrian injuries in children and young adults.

We reviewed the English language scientific literature about equestrian injuries among children and young adults. All studies showed that more females than males were injured, with falls from horses being the most common cause of injury. Fractures were common, and head injuries were associated with the vast majority of deaths (72% to 78%) and hospitalizations (55% to 100%). Although the overall injury rate was low, equestrian athletes are at risk for serious injuries. Pediatricians should know the medical contraindications for participation in equestrian sports and encourage riders to obtain horse safety training and use protective headgear (helmets) approved by the American Society for Testing Materials when riding or working around horses. Pediatricians can play an active role in increasing public awareness of equestrian injuries and in reducing risk of injury.

Adolescent↗

Analysis of structure and transcriptional activation of an osmotin gene.

A Nicotiana tabacum gene encoding the basic PR-like protein osmotin was isolated and characterized. The gene is derived from the N. sylvestris parent of N. tabacum. In cell suspension cultures of tobacco, the osmotin gene was shown to be transcriptionally activated by treatment with ABA. Transcriptional activation of the osmotin promoter was further investigated in transformed plants carrying copies of a fusion of the cloned promoter to the beta-glucuronidase reporter gene. In these plants, the osmotin promoter is transcriptionally activated by the hormones ABA and ethylene. The sensitivity of the osmotin promoter to ABA applied exogenously decreased with age in both roots and shoots of young seedlings. NaCl shock also activated the promoter in plant tissues. The osmotin promoter is much more active in root tissues than in shoot tissues.

Abscisic Acid↗

Social stimuli fail to act as entraining agents of circadian rhythms in the golden hamster.

The ability of social stimuli to act as entraining agents of circadian rhythms was investigated in golden hamsters (Mesocricetus auratus). In a first experiment, pairs of male hamsters (one of them enucleated and the other intact) were maintained under a ligh-dark (LD) cycle with a period of 23.3 h. Running-wheel activity was recorded to determine the effect of social interaction on the free-running circadian rhythm of activity. In several pairs, general activity and body temperature were also recorded. In all pairs the intact animals entrained to the LD cycle, whereas the activity rhythms of the enucleated animals free-ran with periods of approximately 24 h and showed no apparent sign of synchronization or relative coordination with the other member of the pair. In a second experiment, male hamsters maintained in constant darkness received pulses of social interaction, which have been reported to induce phase shifts of the activity rhythm. Consistent phase shifts in the running-wheel activity rhythm were not induced by the social pulses in our experiment. These results suggest strongly that social stimuli are not effective entraining agents of circadian rhythms in the golden hamster.

Animals↗

Osmotin gene expression is posttranscriptionally regulated.

Accumulation of both osmotin mRNA and osmotin protein in tissues of tobacco (Nicotiana tabacum L. var Wisconsin 38) is subject to complex developmental control. Osmotin was found to be most abundant in tobacco roots and in tissues of the outer stem comprised primarily of epidermis, and it was less abundant in the corolla. It was a minor protein in other tissues and was undetectable in some tissues, including those of developing and mature seeds. The mRNA abundances did not always reflect the amount of protein accumulation because in some tissues high levels of mRNA but not protein were measured and vice versa. Accumulation of osmotin mRNA but not protein occurred in some plant tissues due to treatment with abscisic acid, wounding, and tobacco mosaic virus infection. Ethylene induced the accumulation of osmotin mRNA and, to a small extent, protein in seedlings, but was ineffective with cultured cells. Exposure of cultured cells and plants to NaCl caused high levels of both mRNA and the protein to accumulate. Thus, the accumulation of osmotin mRNA is controlled developmentally and by at least five hormonal or environmental signals. However, posttranscriptional processes can limit osmotin accumulation.

Journal Article↗

Expression of Osmotin-Like Genes in the Halophyte Atriplex nummularia L.

A peptide (molecular mass 50 kilodaltons) that is immunologically related to tobacco osmotin was detected in cells of the halophyte Atriplex nummularia. This protein was constitutively expressed in both unadapted and NaCl-adapted cells. A predominant osmotin-like peptide (molecular mass 24 kilodaltons) was also found in culture media after cell growth. Two unique A. nummularia cDNA clones, pA8 and pA9, encoding osmotin-like proteins have been isolated. The pA8 and pA9 inserts are 952 and 792 base pairs and encode peptides of 222 and 224 amino acids, respectively. The peptide deduced from pA8 has a molecular mass of 23,808 daltons and theoretical isoelectric point of 8.31, whereas the peptide derived from pA9 has a molecular mass of 23,827 daltons and an isoelectric point of 6.88. Unique transcripts were detected by the inserts of the cDNA clones, two (1.2 and 1.0 kilobases) by pA8 and one (0.9 kilobase) by pA9. The pA8 transcripts were constitutively accumulated in unadapted and NaCl-adapted cells, whereas the mRNA levels were up-regulated by abscisic acid treatment. The level of pA9 mRNA was induced by NaCl treatment and increased in cells as a function of NaCl adaptation. Southern analysis of the genomic DNA indicated the presence of osmotin-like multigene families in A. nummularia.

Journal Article↗

Alcohol as a risk factor for fall injury events among elderly persons living in the community.

OBJECTIVE: To determine if alcohol use is a risk factor for fall injury events among community-dwelling older persons. DESIGN: Case-control study. SETTING: South Miami Beach, Florida. PARTICIPANTS: 320 persons 65 or older who sought treatment at six area hospitals for injuries resulting from falls; 609 controls, matched for sex and age, selected randomly from Health Care Financing Administration (Medicare) files. MAIN INDEPENDENT VARIABLES: Self-reported current alcohol use. RESULTS: No association was found between fall injury events and average weekly alcohol use. CONCLUSIONS: Further efforts at reducing injuries to older persons from falls should concentrate on other modifiable risk factors, including adequate treatment of underlying medical conditions, reducing inappropriate psychotropic medication use, and installing safety devices in the home.

Accidental Falls↗

Comparison of visual sensitivity for suppression of pineal melatonin and circadian phase-shifting in the golden hamster.

Visual sensitivity for light suppression of pineal melatonin was measured in golden hamsters using 300 s stimuli of monochromatic light (503 nm) in constant darkness. Increasing stimulus irradiance caused a monotonic decrease in pineal-melatonin content. Irradiance greater than 3.5 X 10(10) photons cm-2.s-1 caused significant reductions of melatonin in the hamster pineal. Saturation of the response occurred above 10(11) photons cm-2.s-1 and melatonin levels were suppressed to approximately 7% of levels measured in unstimulated animals. Using a 4-parameter Naka-Rushton function to fit the data, the half-saturation constant for suppression of pineal melatonin was 1.3 x 10(10) photons cm-2.s-1. The sensitivity of the photic-entrainment pathway for circadian rhythms has also been measured in the hamster using identical stimulus parameters. Light suppression of pineal melatonin was 25 times (1.4 log units) more sensitive to irradiance than the phase-shifting response measured for the circadian rhythm of running-wheel activity (comparing the half-saturation constants for the two responses). Both of these responses, however, are much less sensitive to light than other visual responses measured behaviorally in the golden hamster.

Animals↗

A new method for carbon isotopic analysis of protein.

The reaction of ninhydrin with amino acids can be used in carbon isotopic studies of protein. The reaction can be applied to extract as carbon dioxide only peptide-bonded carbon in proteinaceous material, thus avoiding most, if not all, contaminants. Test radiocarbon dates on ancient bone indicate that the method provides reliable ages, and stable carbon isotopic data suggest that our understanding of isotopic dietary reconstruction needs detailed examination. The technique should also be useful in biochemical tracing experiments and in global carbon budget studies, and the underlying principle may be applicable to other isotopes and molecules.

Animals↗

NaCl Regulation of Tonoplast ATPase 70-Kilodalton Subunit mRNA in Tobacco Cells.

A cDNA clone encoding the 70-kilodalton subunit of the tobacco (Nicotiana tabacum var Wisconsin 38) tonoplast ATPase has been isolated. The 1.656 kilobase insert contains only open reading frame that represents more than 80% of the carrot cDNA coding region. The deduced amino acid sequence has greater than 95% sequence identity with the homologous carrot sequence. A transcript of approximately 2.7 kilobase was detected on Northern blots of tobacco poly(A)(+) selected or total RNA using labeled probe produced from this clone. The gene was expressed throughout the growth cycle in unadapted and 428 millimolar NaCl adapted cells. Transcription of the 70-kilodalton subunit gene or mRNA stability was induced by short-term NaCl treatment in NaCl adapted cells or by abscisic acid treatment in both adapted and unadapted cells. Southern analysis indicated the presence of up to four genes encoding the 70-kilodalton subunit.

Journal Article↗

Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus).

1. Light-induced phase shifts of the circadian rhythm of wheel-running activity were used to measure the photic sensitivity of a circadian pacemaker and the visual pathway that conveys light information to it in the golden hamster (Mesocricetus auratus). The sensitivity to stimulus irradiance and duration was assessed by measuring the magnitude of phase-shift responses to photic stimuli of different irradiance and duration. The visual sensitivity was also measured at three different phases of the circadian rhythm. 2. The stimulus-response curves measured at different circadian phases suggest that the maximum phase-shift is the only aspect of visual responsivity to change as a function of the circadian day. The half-saturation constants (sigma) for the stimulus-response curves are not significantly different over the three circadian phases tested. The photic sensitivity to irradiance (1/sigma) appears to remain constant over the circadian day. 3. The hamster circadian pacemaker and the photoreceptive system that subserves it are more sensitive to the irradiance of longer-duration stimuli than to irradiance of briefer stimuli. The system is maximally sensitive to the irradiance of stimuli of 300 s and longer in duration. A quantitative model is presented to explain the changes that occur in the stimulus-response curves as a function of photic stimulus duration. 4. The threshold for photic stimulation of the hamster circadian pacemaker is also quite high. The threshold irradiance (the minimum irradiance necessary to induce statistically significant responses) is approximately 10(11) photons cm-2 s-1 for optimal stimulus durations. This threshold is equivalent to a luminance at the cornea of 0.1 cd m-2. 5. We also measured the sensitivity of this visual pathway to the total number of photons in a stimulus. This system is maximally sensitive to photons in stimuli between 30 and 3600 s in duration. The maximum quantum efficiency of photic integration occurs in 300 s stimuli. 6. These results suggest that the visual pathways that convey light information to the mammalian circadian pacemaker possess several unique characteristics. These pathways are relatively insensitive to light irradiance and also integrate light inputs over relatively long durations. This visual system, therefore, possesses an optimal sensitivity of 'tuning' to total photons delivered in stimuli of several minutes in duration. Together these characteristics may make this visual system unresponsive to environmental 'noise' that would interfere with the entrainment of circadian rhythms to light-dark cycles.

Animals↗

Photic and circadian regulation of c-fos gene expression in the hamster suprachiasmatic nucleus.

Photic information entrains a circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the mammalian hypothalamus to environmental light/dark cycles. To determine whether light regulates c-fos gene expression in the SCN, we have measured c-fos mRNA levels in the SCN of the golden hamster. We report that, during the subjective night, light causes a rapid increase in levels of c-fos mRNA in the SCN. Light pulses of 5 min duration are sufficient to induce c-fos mRNA, and the highest mRNA levels occur 30 min following the onset of light. The minimum level of illumination required to induce an increase in c-fos mRNA is indistinguishable from the minimum irradiance that produces a phase shift in the hamster's circadian rhythm of activity. In addition, the induction of c-fos mRNA in the SCN by light is itself under circadian regulation. Light induction of c-fos mRNA occurs only during the subjective night, at circadian times when photic phase shifting of activity occurs. Taken together, these data suggest that c-fos may be a molecular component of the photic pathway for entrainment of mammalian circadian rhythms.

Animals↗

Accelerator mass spectrometry in biomedical dosimetry: relationship between low-level exposure and covalent binding of heterocyclic amine carcinogens to DNA.

Accelerator mass spectrometry (AMS) is used to determine the amount of carcinogen covalently bound to mouse liver DNA (DNA adduct) following very low-level exposure to a 14C-labeled carcinogen. AMS is a highly sensitive method for counting long-lived but rare cosmogenic isotopes. While AMS is a tool of importance in the earth sciences, it has not been applied in biomedical research. The ability of AMS to assay rare isotope concentrations (10Be, 14C, 26Al, 41Ca, and 129I) in microgram amounts suggests that extension to the biomedical sciences is a natural and potentially powerful application of the technology. In this study, the relationship between exposure to low levels of 2-amino-3,8-dimethyl[2-14C]imidazo[4,5-f]quinoxaline and formation of DNA adducts is examined to establish the dynamic range of the technique and the potential sensitivity for biological measurements, as well as to evaluate the relationship between DNA adducts and low-dose carcinogen exposure. Instrument reproducibility in this study is 2%; sensitivity is 1 adduct per 10(11) nucleotides. Formation of adducts is linearly dependent on dose down to an exposure of 500 ng per kg of body weight. With the present measurements, we demonstrate at least 1 order of magnitude improvement over the best adduct detection sensitivity reported to date and 3-5 orders of magnitude improvement over other methods used for adduct measurement. An additional improvement of 2 orders of magnitude in sensitivity is suggested by preliminary experiments to develop bacterial hosts depleted in radiocarbon. Expanded applications involving human subjects, including clinical applications, are now expected because of the great detection sensitivity and small sample size requirements of AMS.

Animals↗