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PubMed2006

Structural basis for D-amino acid transamination by the pyridoxal 5'-phosphate-dependent catalytic antibody 15A9.

Antibody 15A9, raised with 5'-phosphopyridoxyl (PPL)-N(epsilon)-acetyl-L-lysine as hapten, catalyzes the reversible transamination of hydrophobic D-amino acids with pyridoxal 5'-phosphate (PLP). The crystal structures of the complexes of Fab 15A9 with PPL-L-alanine, PPL-D-alanine, and the hapten were determined at 2.3, 2.3, and 2.5A resolution, respectively, and served for modeling the complexes with the corresponding planar imine adducts. The conformation of the PLP-amino acid adduct and its interactions with 15A9 are similar to those occurring in PLP-dependent enzymes, except that the amino acid substrate is only weakly bound, and, due to the immunization and selection strategy, the lysine residue that covalently binds PLP in these enzymes is missing. However, the N-acetyl-L-lysine moiety of the hapten appears to have selected for aromatic residues in hypervariable loop H3 (Trp-H100e and Tyr-H100b), which, together with Lys-H96, create an anion-binding environment in the active site. The structural situation and mutagenesis experiments indicate that two catalytic residues facilitate the transamination reaction of the PLP-D-alanine aldimine. The space vacated by the absent L-lysine side chain of the hapten can be filled, in both PLP-alanine aldimine complexes, by mobile Tyr-H100b. This group can stabilize a hydroxide ion, which, however, abstracts the C alpha proton only from D-alanine. Together with the absence of any residue capable of deprotonating C alpha of L-alanine, Tyr-H100b thus underlies the enantiomeric selectivity of 15A9. The reprotonation of C4' of PLP, the rate-limiting step of 15A9-catalyzed transamination, is most likely performed by a water molecule that, assisted by Lys-H96, produces a hydroxide ion stabilized by the anion-binding environment.

Alanine Transaminase↗

PubMed1999

Estimating the magnitude of close-up work in school-age children: a comparison of questionnaire and diary instruments.

BACKGROUND: Numerous scientists have noted a relationship between close-up work and myopia. METHODS: A questionnaire and four 24-hour diaries were developed to estimate close-up work activity in a cohort study of close-up work and myopia progression in Singapore children. The number of hours per day that children engaged in each type of close-up work activity over a weekday and weekend during the school term, during the examination period, and in the vacation were estimated. RESULTS: The children spent an average of 6.6 hours per day on total weighted average close-up work, of which 4.3 hours were spent on reading and writing. The intra-class correlation coefficient for the reproducibility of the questionnaire was 0.87 (95% CI 0.85-0.91). The intra-class correlation coefficient for total weighted close-up work was 0.50 (95% CI 0.34-0.66) when the questionnaire was compared with the four 24-hour diaries. The amount of close-up work activity increased with age. CONCLUSIONS: A questionnaire for close-up work was developed and proven to be reproducible and comparable to four 24-hour diaries.

Activities of Daily Living↗

PubMedDate not supplied

Human exposure to elemental mercury in a contaminated residential building.

Residents of a condominium building in Hoboken, New Jersey, were exposed to mercury contamination in indoor air. Elevated levels of mercury were detected in urine samples provided by the residents, and 69% of the urine mercury levels were 20 microg/l or greater. Urine mercury levels were correlated positively with the duration of residency in the building and with the time (i.e., h/d) residents spent in the building. Environmental and biomonitoring data indicated that the residents were being exposed to mercury levels that were cause for health concern. Local health authorities, therefore, declared the building to be unfit for habitation and ordered that the premises be vacated. Health officials monitored the personal belongings of residents for mercury contamination before the items were removed from the building. The residents were offered medical evaluations and support services as part of the relocation effort.

Adult↗

PubMed2000

Cognitive organization of favorable and unfavorable beliefs about performing a behavior.

Intentions to perform behaviors are influenced by beliefs about their consequences, but researchers have not addressed how such beliefs are cognitively organized. In 3 experiments, the authors tested the hypothesis that beliefs are organized according to whether they are favorable or unfavorable in regard to performing a behavior. In Experiment 1, a group of U.S. students first read a list of beliefs favorable and unfavorable to going to a vacation resort and then listed their beliefs about condom use. In Experiment 2, another group of U.S. students listed their beliefs about condom use. In Experiment 3, a 3rd group of U.S. students listed their beliefs about a novel behavior (asking the experimenter for candy). The results of all 3 experiments were consistent with the hypothesis that people cognitively organize their beliefs according to whether they are favorable or unfavorable to the behavior in question.

Attitude↗

PubMed1983

Altitude illness. The dangers of the heights and how to avoid them.

Altitude illness, caused by lack of oxygen, manifests itself in several forms, including acute mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema. The first of these is usually minor, but the second and third can be fatal unless promptly diagnosed and treated (descent being the most effective management). Other, more specific, problems such as high-altitude retinal hemorrhage and thrombophlebitis can also occur in some individuals. Even so, there are only a few medical reasons to deprive an ambulatory, well-compensated patient of a visit to moderate altitude, and the conscientious physician will weigh carefully the risks against the benefits of a vacation in a beautiful and inspiring mountain setting.

Altitude Sickness↗

PubMed1998

Phlebotomus-transmitted toscana virus infections of the central nervous system: a seven-year experience in Tuscany.

Toscana virus (TOSv) is a recently discovered Phlebotomus-transmitted human pathogen involved in acute infections of the central nervous system (CNS) occurring during the summer in natural foci in Italy. The purpose of this prospective study was to investigate the role of this virus in 170 patients with meningitis-meningoencephalitis of suspected viral origin, admitted to the Departments of Infectious Diseases at the Siena Hospital from 1990 to 1996. Infections caused by tick-borne encephalitis virus (TBEv) and TOSv or other neurotropic viruses were routinely diagnosed by means of conventional virological methods. 89 cases were attributed to TOSv, about 10% of which were Europeans on vacation in Tuscany. All of the TOSv-positive cases were observed during the summer and were residents of hilly areas in Siena and its province at an altitude not above 500 m. An increase in the number of cases was observed over the years, with a higher incidence among younger people. The clinical picture was similar to that observed in other viral infections of the CNS. Evolution was benign in all cases; in 2 subjects symptoms and signs of encephalitis were present.

Acute Disease↗

PubMed1993

Louse-borne relapsing fever in Ethiopian children: a clinical study.

An outbreak of louse-borne relapsing fever, caused by the return to their original recruitment areas of soldiers at the end of 30 years of fighting in northern Ethiopia, was reported in the Arsi region. We studied 103 infants and children with louse-borne relapsing fever who were admitted to Asella Hospital between 1 May 1991 and 30 April 1992. Twenty-one per cent of the patients had a clear history of contact with sick ex-soldiers; 42% were students admitted to the hospital following the re-opening of schools after the summer vacation. The common clinical features of the disease were fever in 100%, headache in 84.5%, chills in 74%, abdominal pain in 51%, epistaxis in 20%, hepatomegaly in 26%, splenomegaly in 14%, petechial rash in 34% and jaundice in 10%. Differences in symptoms and signs according to age are described. Observed complications were pneumonia in 14% and central nervous system involvement in 10%. Four children went into deep coma, and two of them died. Severe disease was associated with a high density of spirochaetes in blood smears. Patients were treated with two low doses of penicillin or one dose of penicillin followed by, according to age, chloramphenicol or tetracycline, and with intravenous fluids. The case fatality rate was 1.9%. Jarisch-Herxheimer reactions occurred in 61% of patients. There were relapses in 2.9% of treated patients.

Adolescent↗

PubMed1989

Salivary IgA is a weak stress marker.

Several studies support the hypothesis that psychological stress may negatively affect immunocompetence. The present study sought to determine whether a relationship can be established between a measure of psychological state of stress and level of immunoglobulin of the A class (IgA) in saliva. To this end, 44 dentistry students were tested on four occasions; two occasions were stress inductive (examination situation), and two occasions were free of any academic stressor. At each session, the participants were asked to fill out the stress rating instrument, and unstimulated whole saliva samples were obtained. Salivary IgA was measured by a microplate Enzyme Linked Immunosorbent Assay (ELISA). A significant difference in the level of salivary IgA was observed only for the most polarized contrast, ie, between final exam and end of summer vacation (p less than .01). A weak negative correlation between the level of salivary IgA and the stress rating was observed (r = -0.25) only at the final exam. Our results suggest that assaying immunoglobulin A in saliva to measure stress may not be as useful in psychophysiological research as expected.

Adult↗

PubMed2000

Heavy metals in urban soils of East St. Louis, IL, Part I: Total concentration of heavy metals in soils.

The city of East St. Louis, IL, has a history of abundant industrial activities including smelters of ferrous and non-ferrous metals, a coal-fired power plant, companies that produce organic and inorganic chemicals, and petroleum refineries. A protocol for soil analysis was developed to produce sufficient information on the extent of heavy metal contamination in East St. Louis soils. Soil cores representing every borough of East St. Louis were analyzed for heavy metals--As, Cd, Cu, Cr, Hg, Ni, Pb, Sb, Sn, and Zn. The topsoil contained heavy metal concentrations as high as 12.5 ppm Cd, 14,400 ppm Cu, ppm quantities of Hg, 1860 ppm Pb, 40 ppm Sb, 1130 ppm Sn, and 10,360 ppm Zn. Concentrations of Sb, Cu, and Cd were well correlated with Zn concentrations, suggesting a similar primary industrial source. In a sandy loam soil from a vacated rail depot near the bank of the Mississippi River, the metals were evenly distributed down to a 38-cm depth. The clay soils within a half-mile downwind of the Zn smelter and Cu products company contained elevated Cd (81 ppm), Cu (340 ppm), Pb (700 ppm), and Zn (6000 ppm) and displayed a systematic drop in concentration of these metals with depth. This study demonstrates the often high concentration of heavy metals heterogeneously distributed in the soil and provides baseline data for continuing studies of heavy metal soil leachability.

Hydrogen-Ion Concentration↗

PubMed2002

Teaching and learning about bioscience ethics with undergraduates.

Bioscience ethics acts as a practical interface between science and bioethics. It links scientific endeavour and its application into adaptive forms of bioethical consensus. Its major elements are increased understanding of biological systems, responsible use of technology, and curtailment of ethnocentric debates in tune with new scientific insights. This paper briefly describes the students' learning experience gained from the vacation unit BIOL 240, Introduction to Bioscience Ethics, as taught in biology, Macquarie University. On the basis of our evidence students were overwhelmingly positive about their learning because the unit assisted them to better face dilemmas that arise from the application of science and technology. The structure also provided active engagement with the subject matter and preferred learning environments that supported and contested their understanding of concepts relevant to bioscience and bioethics.

Journal Article↗

PubMed2006

Seasonal variations in the initiation of smoking among adolescents.

Numerous studies have identified a variety of reasons that youths give for starting smoking. Few efforts have been made, however, to identify seasonal variations in initiation. This study was an attempt to fill that void. We examined data from 342 youths participating in a mandated smoking education and cessation program in Texas. Data were collected based on responses to questions in participant workbooks, including an item asking participants about the month in which they started smoking. A total of 47% of the participants indicated that they started smoking in May through August (chi2 = 91.42, df = 3). Post-hoc analyses indicated that significantly more youths than expected began smoking in May and June, whereas significantly fewer youths than expected began smoking in September and November. Unsupervised time out of school during the first months of summer vacation is a period of increased danger for smoking initiation. The significantly lower rates during September seem to be related to the beginning of school.

Activities of Daily Living↗

PubMed2005

Conservation of eubacterial replicases.

The last 15 years of effort in understanding bacterial DNA replication and repair has identified that the donut shaped beta2 sliding clamp is harnessed by very functionally different DNA polymerases throughout the lifecycle of the bacterial cell. Remarkably, the sites of binding of these polymerases, in most cases, appear to be the same shallow pocket on the beta dimer. In every case, binding of beta2 by the polymerase enhances their processivity of DNA synthesis. This binding site is also the same point of interaction between beta2 and the clamp loader complex, which binds beta2, opens and places it onto the DNA strand and then vacates the site. Beta2 may also be involved in the initiation of DNA replication again via contact through this same site. While much of the research effort has focused on Escherichia coli and Bacillus subtilis, conservation of this complex system is becoming apparent in diverse bacteria.

Bacteria↗

PubMed2005

Scope and patterns of tourist injuries in the European Union.

European Union (EU) countries are among the leading tourist destinations in the world. Despite growing consumer demands on the safety of travelling, injuries amongst tourists remain an essentially invisible problem. Unique national and regional data sources are the only means by which the important negative impact of injuries on the health of non-domestic tourists in the EU-15 is underlined. With an estimated number of 3800 tourists dying each year, injuries account for up to 30% of fatalities during vacation. This toll reflects an increased risk of mortality in tourists compared to the domestic population. Amendments to national and EU health and injury monitoring are suggested in order to enable authorities to examine personal risks to travellers in more detail.

Adolescent↗

PubMedDate not supplied

Seasonality of first coitus in the United States.

Recent attention to causes of seasonality of births leads to an interest in seasonality patterns in the antecedents to birth, including gestational length, conception, and coital activity. In this paper we study the beginning of the process: first intercourse among adolescents and young adults. Analysis of a small and local dataset is suggestive that loss of virginity is particularly likely during the summer. A test of this "Summer Vacation Theory" using a large national dataset supports the generality of the phenomenon. Further, a prediction that seasonality patterns will change during the transition from high school to work and college is tested and supported. The existence of both biological and psycho-social mechanisms is suggested. Policy implications are reviewed.

Adolescent↗

PubMed2004

Association of sickness absence with poor sleep and depressive symptoms in shift workers.

A cross-sectional study was conducted to evaluate the contribution of daily sleep habits and depressive symptoms to sickness absences of shift workers. A self-administered questionnaire that solicited answers about sleep, symptoms of depression, sickness absence, diseases/injuries, and lifestyle factors was submitted to a sample of 522 rotating shift workers between the ages of 18-59 (mean 27) yrs of an electric equipment manufacturing company. The seven features of sleep queried were daily hours of sleep, time to fall asleep, awakening during sleep, early morning awakening, sleep well at night, sufficiency of sleep, and excessive daytime sleepiness at work. The responses were assessed over the subject's previous 1-yr period. Each sleep feature, except daily sleeping hours, was dichotomized by the following responses: (1) taking more than 30min to fall asleep (difficulty initiating sleep; DIS), (2) awakening during sleep almost every day (difficulty maintaining sleep; DMS), (3) early morning awakening almost every day (EMA), (4) sleeping very poorly or not so well at night, (5) definite or somewhat insufficient nightly sleep, and (6) excessive daytime sleepiness at work almost every day (EDS). Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Sickness absence was calculated by asking subjects "How many days in total have you been absent from work due to sickness, including paid vacation, in the last 1-yr period?" The responses were divided into three groups that included no (0 days) sickness absences (reference group, n=235 subjects), 1 to 4 days (short-term, n=199 subjects), and 5 days or more (long-term, n = 88 subjects). Compared to the prevalence of sleep features of the reference group, workers with short-term absence showed a significantly higher prevalence of EMA with an odds ratio (OR) of 5.3, 95% confidence interval (CI) 1.3-22.0. Long-term absence was significantly associated with DMS (OR = 2.1, 95%CI 1.0-4.6), EMA (OR = 5.6, 95%CI 1.0-28.7), sleeping poorly at night (OR= 2.6, 95%CI 1.4-5.0), and high depressive symptoms (OR = 2.0, 95%CI 1.0-3.7) according to the CES-D score of >16, after adjusting for multiple confounding variables. These data point to an association between both the parameters of poor sleep and symptoms of deep depression when self-reported sickness absence is frequent. The association is particularly strong with long-term absence in male shift workers.

Adolescent↗

PubMed1994

Globular and asymmetric acetylcholinesterase in the synaptic basal lamina of skeletal muscle.

The aim of this study was to characterize the molecular forms of acetylcholinesterase (AChE) associated with the synaptic basal lamina at the neuromuscular junction. The observations were made on the neuromuscular junctions of cutaneous pectoris muscles of frog, Rana pipiens, which are similar to junctions of most other vertebrates including mammals, but are especially convenient for experimentation. By measuring relative AChE activity in junctional and extrajunctional regions of muscles after selective inactivation of extracellular AChE with echothiophate, or of intracellular AChE with DFP and 2-PAM, we found that > 66% of the total AChE activity in the muscle was junction-specific, and that > 50% of the junction-specific AChE was on the cell surface. More than 80% of the cell surface AChE was solubilized in high ionic strength detergent-free buffer, indicating that most, if not all, was a component of the synaptic basal lamina. Sedimentation analysis of that fraction indicated that while asymmetric forms (A12, A8) were abundant, globular forms sedimenting at 4-6 S (G1 and G2), composed > 50% of the AChE. It was also found that when muscles were damaged in various ways that caused degeneration of axons and muscle fibers but left intact the basal lamina sheaths, the small globular forms persisted at the synaptic site for weeks after phagocytosis of cellular components; under certain damage conditions, the proportion of globular to asymmetric forms in the vacated basal lamina sheaths was as in normal junctions. While the asymmetric forms required high ionic strength for solubilization, the extracellular globular AChE could be extracted from the junctional regions of normal and damaged muscles by isotonic buffer. Some of the globular AChE appeared to be amphiphilic when examined in detergents, suggesting that it may form hydrophobic interactions, but most was non-amphiphilic consistent with the possibility that it forms weak electrostatic interactions. We conclude that the major form of AChE in frog synaptic basal lamina is globular and that its mode of association with the basal lamina differs from that of the asymmetric forms.

Acetylcholinesterase↗

PubMed1953

Mitochondria in the flight muscles of insects. II. Effects of the medium on the size form, and organization of isolated sarcosomes.

1. The sarcosomes of Drosophila and the blowfly, Phormia, are dense, spherical, homogeneous bodies when isolated from flight muscle and promptly examined under the phase contrast, oil immersion objective. 2. Their average diameter in newly emerged flies is about 1 micro. This value increases rapidly during the 1st week of adult life and then becomes constant at approximately 2.5 micro. At each age the variation in sarcosome diameter conforms approximately to a normal distribution. 3. The degree to which isolated sarcosomes retain their initial size and organization is remarkably conditioned by the composition and the hydrogen ion concentration of the medium in which they are teased and suspended. In suboptimal media three major categories of change were encountered: (1) swelling, with or without compaction of the contents (as in distilled water and salt solutions); (2) shrinkage to rod-like, pleomorphic forms (as in blood serum); and (3) fuzzy degeneration (as in sugar solutions). 4. The membrane that surrounds each sarcosome becomes plainly visible in swollen sarcosomes. A continuation of swelling is accompanied by the escape of the sarcosomal contents, the vacated membrane persisting as a spherical, optically empty ghost. 5. Sarcosomes appear to behave like osmometers when suspended in various aqueous solutions. Solutes which penetrate the membrane show only transient effects in preventing the osmotic entry of water. 6. Under this analysis we find the membrane to be more or less freely permeable to the ions of sodium, potassium, calcium, magnesium, chloride, and phosphate, to non-electrolytes smaller than hexoses, to phosphorylated hexoses, and to several intermediates of the citric acid cycle. 7. The sarcosomal membrane appears to be less permeable to non-electrolytes larger than pentoses, provided that such molecules are not phosphorylated. 8. The membrane shows a higher permeability to ATP than to ADP. The significance of this observation is considered with respect to the ADP-ATP shuttle between sarcosomes and muscle fibrils. 9. Simple solutions of electrolytes or non-electrolytes cause more or less conspicuous changes in the microscopic appearance of sarcosomes. Prolonged preservation was achieved only in more complicated media containing protein. It is concluded that the Donnan equilibrium is the source of the principal osmotic forces regulating the movement of water through the sarcosomal membrane. 10. The optimal medium for the preservation of isolated sarcosomes was an intracellular Ringer solution containing 2.5 per cent crystalline bovine albumin in 0.16 M potassium phosphate buffer at pH 7.0.

Animals↗

PubMed1977

Sodium ions as blocking agents and charge carriers in the potassium channel of the squid giant axon.

Instantaneous K channel current-voltage (I-V) relations were determined by using internally perfused squid axons. When K was the only internal cation, the I-V relation was linear for outward currents at membrane potentials up to +240 mV inside. With 25-200 mM Na plus 300 mM K in the internal solution, an N-shaped I-V curve was seen. Voltage-dependent blocking of the K channels by Na produces a region of negative slope in the I-V plot (F. Bezanilla and C. M. Armstrong. 1972. J. Gen Physiol, 60: 588). At higher voltages (greater than or equal to 160 mV) we observed a second region of increasing current and a decrease in the fraction of the K conductance blocked by Na. Internal tetraethylammonium (TEA) ions blocked currents over the whole voltage range. In a second series of experiments with K-free, Na-containing internal solutions, the I-V curve turned sharply upward about +160 mV. The current at high voltages increased with increasing internal Na concentration was largely blocked by internal TEA. These data suggest that the K channel becomes substantially more permeable to Na at high voltages. This change is apparently responsible for the relief, at high transmembrane voltages, of the blocking effect seen in axons perfused with Na plus K mixtures. Each time a Na ion passed through, vacating the blocking site, the channel would transiently allow K ions to pass through freely.

Animals↗