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Biomedical subjects

J M Roper

Publications and source records attributed to J M Roper.

At least 19 recordsLinked to original sources
PubMed2004

Health and environmental testing of manganese exhaust products from use of methylcyclopentadienyl manganese tricarbonyl in gasoline.

This paper reviews recent research on the environmental effects of methylcyclopentadienyl manganese tricarbonyl (MMT), personal exposures to airborne Mn as a result of MMT use, chemical characterization of the manganese particulates emitted from the tailpipe and progress in developing a (PBPK) model for manganese in rodents. Recent studies show that manganese is emitted as a mixture of compounds with an average valence of about 2.2. The major products are sulfate, phosphate, and smaller amounts of oxides. Because only small amounts of Mn are used in gasoline (<18 mg Mn/gal) and less than 15% of the combusted Mn is emitted, soil along busy roads is not elevated in Mn, even after long-term use of MMT. A very large population-based study of manganese exposures in the general population in Toronto, where MMT has been used continuously for over 20 years, showed that manganese exposures were quite low, the median annual exposure was 0.008 microg Mn/m(3). A great amount of toxicological research on Mn has been carried out during the past few years that provides data for use in developing a PBPK model in rodents. These data add greatly to the existing body of knowledge regarding the relationship between Mn exposure and tissue disposition. When complete, the PBPK model will contribute to our better understanding of the essential neurotoxic dynamics of Mn.

Animals↗
PubMed2001

Bioaccumulation of butyltins in Dreissena polymorpha at a confined placement facility in Buffalo, New York.

This study involves a site characterization followed by biomonitoring with the zebra mussel, Dreissena polymorpha, at the Times Beach confined placement facility (CPF), located in Buffalo, NY. The contaminant of interest was tributyltin (TBT) and the degradation products dibutyltin (DBT) and monobutyltin (MBT). At study initiation (Day 0) TBT levels in the baseline mussels were 5.86 +/- 0.43 ng Sn/g, DBT levels were 2.25 +/- 0.37 ng Sn/g. No MBT was detected in the Day 0 baseline samples. Caged reference mussels placed back in the Black Rock Channel Lock and retrieved on Days 19 and 34 had TBT, DBT, and MBT levels which did not differ significantly from the Day 0 baseline levels. Mussels placed at the Times Beach CPF had TBT concentrations that were significantly lower at both Days 19 (3.65 +/- 0.90 ng Sn/g) and 34 (3.50 +/- 1.03 ng Sn/g) than the Day 0 baseline analysis (5.86 +/- 0.43 ng Sn/g). The results of this study indicate that butyltins were detected at the CPF site in the sediment (7.33 +/- 5.70 ng Sn/g) but not the water column (not detected at 0.01 microgram/l). In this study the zebra mussel was able to depurate TBT even in the presence of contaminated sediment. TBT may be bioaccumulated from the sediments. However, the initial levels in the mussels were so high, levels actually dropped as sediment-tissue equilibria levels were reached by the mussels.

Analysis of Variance↗
PubMed2001

Nurse caregiver feelings about agitation in Alzheimer's disease.

This study examines the feelings of nurse caregivers of patients with Alzheimer's disease (AD) who are agitated. Methods included participant observation, examination of medical records, and ethnographic interviews of 17 nurse caregivers from one inpatient setting. Two patterns of feelings emerged from the data. One pattern was associated with caregiver expressions of personal identification with and vulnerability to AD. These nurses endorsed feelings of helplessness, men hopelessness, and frustration when providing care to agitated AD patients. A second pattern situated nursing interactions within the realistic context of the patient's response to the illness. Caregiver feelings of confidence, competence, and satisfaction were associated with the second pattern. The relationship between the feeling states of nurse caregivers and their reported management of agitation in AD is discussed. Recognition and awareness of distressing feelings is a necessary first step for nurses to learn less personalized reactions to patients and respond more objectively to agitated behaviors.

Aged↗
PubMed2000

The enigma of cobalamin (Vitamin B12) biosynthesis in Porphyromonas gingivalis. Identification and characterization of a functional corrin pathway.

The ability of Porphyromonas gingivalis to biosynthesize tetrapyrroles de novo has been investigated. Extracts of the bacterium do not possess activity for 5- aminolevulinic-acid dehydratase or porphobilinogen deaminase, two key enzymes involved in the synthesis of uroporphyrinogen III. Similarly, it was not possible to detect any genetic evidence for these early enzymes with the use of degenerate polymerase chain reaction. However, the bacterium does appear to harbor some of the enzymes for cobalamin biosynthesis since cobyric acid, a pathway intermediate, was converted into cobinamide. Furthermore, degenerate polymerase chain reaction with primers to cbiP, which encodes cobyric-acid synthase, produced a fragment with a high degree of identity to Salmonella typhimurium cbiP. Indeed, the recently released genome sequence data confirmed the presence of cbiP together with 14 other genes of the cobalamin pathway. A number of these genes were cloned and functionally characterized. Although P. gingivalis harbors all the genes necessary to convert precorrin-2 into cobalamin, it is missing the genes for the synthesis of precorrin-2. Either the organism has a novel pathway for the synthesis of precorrin-2, or more likely, it has lost this early part of the pathway. The remainder of the pathway may be being maintained to act as a salvage route for corrin synthesis.

Base Sequence↗
PubMed2000

Psychiatric patients' perceptions of waiting time in the psychiatric emergency service.

Recent customer service surveys have indicated that patients in the Psychiatric Emergency Service (PES) are increasingly dissatisfied with the "waiting" time connected with expanded services. This study examined the impact of six interventions that altered the environment of waiting patients and their resulting perceptions of time spent in PES. The interventions were communication (three styles), relaxing music, educational videos, and recreational activities. Each intervention was conducted for 7 days, followed by 7 days of no intervention. Patients completed a Time Assessment Tool that measured expectations of, perceptions of, and satisfaction with waiting time. These data were compared to actual time, as reflected on the log maintained in the PES. In general, environmental interventions reduced patients' perceived time, compared to no intervention. Significantly, interacting with patients with caring and concern consistently resulted in a reduced perception of waiting time, compared to the other interventions.

Adult↗
PubMed1997

A single precursor protein for ferrochelatase-I from Arabidopsis is imported in vitro into both chloroplasts and mitochondria.

Ferrochelatase is the last enzyme of heme biosynthesis and in higher plants is found in both chloroplasts and mitochondria. We have isolated cDNAs for two isoforms of ferrochelatase from Arabidopsis thaliana, both of which are imported into isolated chloroplasts. In this paper we show that ferrochelatase-I is also imported into isolated pea mitochondria with approximately the same efficiency as into chloroplasts. Processing of the precursor was observed with both chloroplast stroma and mitochondrial matrix extracts. This was inhibited by EDTA, indicating it was due to the specific processing proteases. The specificity of import was verified by the fact that the mitochondrial preparation did not import the precursor of the light-harvesting chlorophyll a/b protein precursor or the precursor of porphobilinogen deaminase, an earlier enzyme of tetrapyrrole biosynthesis, both of which are exclusively chloroplast-located. Furthermore, import of ferrochelatase-I precursor into mitochondria was inhibited by valinomycin, but this had no effect on its import into chloroplasts. Thus a single precursor molecule is recognized by the import machinery of the two organelles. The implications for the targeting of ferrochelatase in a possible protective role against photooxidative stress are discussed.

Arabidopsis↗
PubMed1997

Molecular localisation of ferrochelatase in higher plant chloroplasts.

Within the chloroplast of higher plants, a crucial branchpoint of the tetrapyrrole synthesis pathway is the chelation of either Fe2+ to make haem, or Mg2+ for chlorophyll, catalysed by ferrochelatase or magnesium chelatase, respectively. One model that has been proposed for the control of this branchpoint, based on biochemical studies, is that the two enzymes are spatially separated within the chloroplast, ferrochelatase being exclusively in the thylakoids, while magnesium chelatase is associated with the envelope [Matringe, M., Camadro, J.-M., Joyard, J. & Douce, R. (1994) J. Biol. Chem. 269, 15010-15015]. We have used a sensitive molecular method to investigate this possibility. Radiolabelled precursor proteins for ferrochelatase from Arabidopsis have been imported into isolated chloroplasts. Their distribution in the different subchloroplastic fractions have then been determined, and compared with that for light-harvesting chlorophyll protein, which is exclusively thylakoidal, and the envelope-located phosphate translocator. Clear evidence for the specific association of ferrochelatase protein with both thylakoid and envelope membranes has been obtained, thus suggesting strongly that the control of the branchpoint cannot be by spatial separation of the two chelatases.

Arabidopsis↗
PubMed1997

The reality of political ethical conflicts. Nurse manager dilemmas.

Losing sleep and deciding your administrative job is not worth the pressures you feel could be symptoms that you are struggling with a political ethical conflict. The authors describe a variety of political ethical conflicts and how they can arise, giving examples of dilemmas experienced by nurse managers and offering suggestions for developing successful coping strategies.

Aged↗
PubMed1996

Bioaccumulation of toxicants in the zebra mussel, Dreissena polymorpha, at the Times Beach Confined Disposal Facility, Buffalo, New York.

This study consisted of a site characterization followed by biomonitoring the zebra mussel, Dreissena polymorpha, at the Times Beach Confined Disposal Facility (CDF), located in Buffalo, New York. Concentrations of selected contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and metals -arsenic (As), chromium (Cr), barium (Ba), mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se) and silver (Ag)-were at or below detection limits in the water column. Sediment contaminant concentrations, recorded as dry weight, were as high as 549 mg/kg for total PAHs, 9 mg/kg for PCB Aroclor 1248 and 54, 99, 6, 355, 637 and 16 mg/kg for the metals As, Ba, Cd, Cr, Pb and Hg, respectively. To predict contaminant bioavailability, elutriate and whole sediment toxicity tests were performed utilizing the cladoceran, Daphnia magna. Whole sediment tests indicated significant impact. Control survival was 84%, while sediment treatment had survival ranging from 1 to 7%. Mean control reproduction was 86.8 neonates, whereas treatment reproduction ranged from 1.4 to 9.0. Zebra mussels placed both in the water column (Upper) and at the sediment level (Lower) survived the 34-day exposure. Contaminants that significantly accumulated in zebra mussel tissue (wet wt mg/kg) were total PAHs (6.58), fluoranthene (1.23), pyrene (1.08), chrysene (0.98), benzo(a)anthracene (0.60), PCB Aroclor 1248 (1.64), As (0.97), Cr (2.87) and Ba (7.00). Accumulation of these contaminants in zebra mussel tissue represent a potentially realistic hazard to organisms (i.e. fish and birds) that feed on them.

Journal Article↗
PubMed1995

Isolation, characterisation and expression of a cDNA clone encoding plastid aspartate aminotransferase from Arabidopsis thaliana.

A clone encoding aspartate aminotransferase (AAT, EC 2.6.1.1) was isolated from an Arabidopsis thaliana leaf cDNA library. This clone contains a 1365 bp open reading frame encoding a polypeptide of 49.8 kDa, designated Ataat1. The clone was shown to contain a chloroplastic isoenzyme as an in organellar protein import assay demonstrated that a radiolabelled transcription/translation product of 49.8 kDa was imported into viable pea chloroplasts and was subsequently processed to yield a mature protein of 45 kDa. The open reading frame corresponding to the predicted mature AAT was manipulated into an expression construct (pEC14). Transformed Escherichia coli cells containing pEC14 expressed up to 16 times more AAT activity than vector only controls, thus demonstrating conclusively that the clone encoded AAT.

Amino Acid Sequence↗
PubMed1994

Isolation of a cDNA encoding chloroplast ferrochelatase from Arabidopsis thaliana by functional complementation of a yeast mutant.

Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX to form protoheme. It is located in the mitochondria in all eukaryotes and is also found in plastids in plants. Although it has been purified from animals and microorganisms, and genes for it isolated and characterized, very little is known about plant ferrochelatases. We have isolated a cDNA for ferrochelatase from the higher plant Arabidopsis thaliana by functional complementation of a mutant of Saccharomyces cerevisiae defective in this enzyme. The cDNA encodes a protein of 52 kDa, which has 25-35% sequence similarity to ferrochelatases from other organisms. There is an N-terminal extension of about 65 residues, which is almost certainly the chloroplast transit peptide, since the precursor protein, transcribed and translated in vitro, is efficiently imported and processed to the mature size by isolated pea chloroplasts. In contrast, the precursor was not processed by mitochondrial processing peptidase activity, nor could import into isolated yeast mitochondria be demonstrated conclusively, although, presumably, in the rescued yeast mutant, at least some of the Arabidopsis ferrochelatase must be present in the mitochondria. A single transcript the same size as the cDNA was detected in both Arabidopsis leaves and roots, although the amount of message was greater in the photosynthetic tissue. Southern analysis suggests that there is a single gene for chloroplast ferrochelatase in Arabidopsis.

Amino Acid Sequence↗
PubMed1994

The homicidal patient: when a plan of care violates standards of care.

1. The nursing care of an extraordinarily dangerous patient may necessitate implementing a treatment plan that should never be used under normal circumstances. 2. The subject whose case is described in this article presented management problems that required a plan violating accepted standards of care. 3. Although ultimately successful, the plan's restrictive mode (and the stress of coping with this patient) wearied nursing staff members and caused divisions among the staff and multidisciplinary team.

Adult↗
PubMed1991

The interactional dynamics of violence, Part I: An acute psychiatric ward.

The purpose of the following two articles is to shift the emphasis from a strictly patient-centered focus to an interaction-centered focus. Evidence from independent research projects in two different patient care settings demonstrates the interactional nature of violent behavior. One project was conducted on an acute adult psychiatric inpatient unit; the other project was conducted in a juvenile detention facility. Each of these articles describes one segment from two separate and independent parent research projects. Although these clinical research projects were conducted in two very different clinical facilities with very different patient populations, the researchers subsequently discovered common categories and themes regarding the issues of control and the interactional dynamics of violence in the two studies. Interactions between health care providers and patients in the acute psychiatric setting resembled the corresponding interactions in the juvenile detention setting. Both populations had been deprived of power, and all patients/adolescents had some restrictions on their freedom with few choices and opportunities to display positive conduct. Furthermore, the environment in each setting was structured according to the needs of the staff/caretakers, who assumed some degree of control over the individuals in the population being served. Labeling and control issues were identified in the findings from both studies. In the two articles that follow, the specific qualitative research methods used in each study are described. Common themes are discussed from each clinical perspective, using research data and case examples that exemplify the interactional basis of violent behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Attitude of Health Personnel↗
PubMed1991

Agitation in the demented patient. A framework for management.

The inability to manage agitation has led to institutionalization of the patient by the family, overuse of physical restraints, and inappropriate use of psychotropic medication, all of which confound the behavior of the demented individual. It is not only the behavior of the patient but also the interpretation of that behavior that is critically important in the successful management of agitation. Caregivers must be careful to assess their own reactions and responses to patient behaviors before actions are taken that may not lessen agitation but increase the frequency and intensity of patient action.

Aged↗