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Biomedical subjects

L Nagel

Publications and source records attributed to L Nagel.

13 recordsLinked to original sources
PubMed2006

A simple molecular technique for identifying marine host fish by sequencing blood-feeding parasites.

Gnathiid isopods are common ectoparasites of fish on the Great Barrier Reef, Australia. While screening for appropriate markers for phylogenetic studies of gnathiids, we found that primers for 12S and 16S rDNA preferentially amplified the host fish DNA instead of gnathiid DNA. This amplification occurred even when using gnathiids that were not engorged with host blood and adult gnathiids that do not feed on fish blood. This method could be used in host-parasite studies to identify hosts without having to sample parasites directly from the host (which can be costly and requires considerable skill in a marine environment). Target ribosomal DNA sequences can be amplified from total DNA extracted from parasites that are captured in funnel traps or plankton tows. Sequence data from these can be used to identify the hosts that gnathiids were feeding on before capture.

Animals↗
PubMed2000

Natural selection and parallel speciation in sympatric sticklebacks.

Natural selection plays a fundamental role in most theories of speciation, but empirical evidence from the wild has been lacking. Here the post-Pleistocene radiation of threespine sticklebacks was used to infer natural selection in the origin of species. Populations of sticklebacks that evolved under different ecological conditions show strong reproductive isolation, whereas populations that evolved independently under similar ecological conditions lack isolation. Speciation has proceeded in this adaptive radiation in a repeatable fashion, ultimately as a consequence of adaptation to alternative environments.

Adaptation, Physiological↗
PubMed1996

Students' self-reported substance use by grade level and gender.

Over 900 students in the rural northwest at the fourth, sixth, eighth, and tenth grade levels were surveyed for alcohol and drug use. The survey instrument measured self-reported usage of seventeen substances. The descriptive statistical results are reported by gender as well as grade-level usage rates. Discussion includes targeting drug prevention programs for specific grade and gender levels based upon the results.

Adolescent↗
PubMed1996

Students' self-reported substance use by grade level and gender.

Over 900 students in the rural northwest at the fourth, sixth, eighth, and tenth grade levels were surveyed for alcohol and drug use. The survey instrument measured self-reported usage of seventeen substances. The descriptive statistical results are reported by gender as well as grade-level usage rates. Discussion includes targeting drug prevention programs for specific grade and gender levels based upon the results.

Adolescent↗
PubMed1995

Behavior assessment and cross-validation by surrogate measures in drug prevention research.

When used with more orthodox survey or interview techniques, surrogate measures can enhance a study's credibility. Presented is a case report which illustrates the viability of using a surrogate measure to cross-validate self-reports of alcohol consumption by members of a fraternity at a large Midwestern university. As federal authorities continue to scrutinize myriad ways to reduce the nation's health care burden drug abuse research will have an enhanced opportunity to justify its role in that movement. The historical reliance on self-report methods which lack supportive, corroborating evidence of behavior change may jeopardize preventive drug education's opportunity to play a more integral part in influencing health promotion policies.

Alcohol Drinking↗
PubMed1984

Viroid replication: equilibrium association constant and comparative activity measurements for the viroid-polymerase interaction.

The binding and replication of purified potato spindle tuber viroid (PSTV) by DNA-dependent RNA polymerase II from wheat germ was studied in analytical ultracentrifugation experiments and in vitro transcription assays. The equilibrium association constant for the viroid-polymerase interaction is 1.9 X 10(7) M-1. Both ultraviolet and fluorescent monitoring during the sedimentation experiments showed two distinguishable viroid-polymerase complexes. These are interpreted as resulting from a 1:1 and 2:1 enzyme-to-viroid binding stoichiometry. A265/A280 ratios across the sedimenting boundaries, the sedimentation velocity of the complexes, as well as electron microscopic data support this interpretation. The role of viroid secondary structure in enzyme binding and polymerization is discussed in the light of these results and compared with binding and polymerization data for virusoid RNA, single- and double-stranded RNA, and double-stranded DNA.

Microscopy, Electron↗
PubMed1983

Dynamics and interactions of viroids.

Viroids are single stranded circular RNA molecules of 120,000 daltons which are pathogens of certain higher plants and replicate autonomously in the host cell. Virusoids are similar to viroids in respect to size and circularity but do replicate only as a part of a larger plant virus. The structure and structural transitions have been investigated by thermodynamic, kinetic and hydrodynamic methods and have been compared to results from calculations of the most favorable native structures and the denaturation process. The algorithm of Zuker et al. was modified for the application to circular nucleic acids. For viroids the calculations confirm our earlier theoretical and experimental results about the extended native structure and the highly cooperative transition into a branched structure. Virusoids, although described in the literature as viroid-like, show less base pairing, branching in the native secondary structure, and only low cooperativity during denaturation. They resemble more closely the properties of random sequences with length, G:C content, and circularity as in viroids but sequences generated by a computer. The comparison of viroids, virusoids and circular RNA of random sequences underlines the uniqueness of viroid structure. The interactions of viroids with dye and oligonucleotide-ligands and with RNA-polymerase II from wheat germ, which enzyme replicates viroids in vitro, has been studied in order to correlate viroid structure and its ability for specific interactions. Specificity of the interactions may be interpreted on the basis of the neighbourhood of double stranded and single stranded regions. In the host cell viroids are localized in the cell nucleus; they may be detected as free nucleic acids and in high molecular weight complexes together with other RNA and proteins.

Base Sequence↗
PubMed1979

Mixed and obstructive sleep apnea and near miss for sudden infant death syndrome: 2. Comparison of near miss and normal control infants by age.

Twenty-nine full-term near miss for sudden infant death syndrome (SIDS) and 30 normal control infants underwent 24-hour polygraphic monitoring. Several types of respiratory events during sleep (eg, central, mixed, and obstructive apnea, periodic breathing) were defined and tabulated. Analysis of these respiratory variables and comparison of groups of near miss and control infants indicated that between 3 weeks and 4 1/2 months of age only one variable was consistently different at a statistically significant level: the number of mixed and obstructive apnea greater than 3 seconds during total sleep time. This study also showed an increase in mixed and obstructive respiratory events during sleep at 6 weeks of age in control as well as in near miss infants.

Female↗
PubMed1979

Obstructive sleep apnea and near miss for SIDS: I. Report of an infant with sudden death.

An infant girl followed up from birth to death at the University Medical Center had ""congenital stridor'' and a ""near miss for SIDS'' event at 3 months of age. As part of an ongoing SIDS research project, she underwent 24-hour polygraphic monitoring at 21 weeks of age. Sudden infant death occurred within 30 hours after the polygraphic study. Polygraphic data obtained from this infant are compared with those from control infants and other infants with near miss for SIDS who were of similar ages. The number of mixed and obstructive respiratory events during sleep was abnormally high on the infant's recording. Histologic findings, involving particularly the midline structures of the brain stem, are discussed.

Apnea↗
PubMed1975

Ascorbate and phagocyte function.

Scorbutic guinea pig neutrophils (PMN) were found to produce H2O2 and kill Staphylococcus aureus as well as control PMN, suggesting that ascorbate does not contribute significantly to phagocyte H2O2 production or bacterial killing. Total and reduced ascorbate contents of human PMN was observed to fall upon phagocytosis, whereas dehydroascorbate increased to a lesser extent. These observations are consistent with the view that ascorbate constitutes a functional part of the PMN's redox-active components and may thus function to protect cell constituents from denaturation by the oxidants produced during phagocytosis.

2,3-Diketogulonic Acid↗
PubMedDate not supplied

Practice patterns of acute care nurse practitioners.

This study was undertaken to examine the practice pattern of nurse practitioners employed in Ontario acute care settings. A descriptive design, incorporating quantitative and qualitative methods for data collection, was used. The acute care nurse practitioners' practice pattern varied in terms of scope of practice, model guiding practice, reporting relations, and extent of role implementation. Role implementation encompassed activities representing the four role components: clinical practice, education, administration or management, and research. The acute care nurse practitioners engaged most frequently in the clinical component of the role. They performed medical and advanced nursing functions. They emphasized that they do not work in isolation and that they do not replace physicians or residents.

Acute Disease↗
PubMedDate not supplied

Organizational factors influencing nurse practitioners' role implementation in acute care settings.

The purpose of this study was to explore the influence of organizational factors on the Acute Care Nurse Practitioner (ACNP) role implementation. A descriptive correlational design, incorporating quantitative and qualitative methods for data collection was used. The sample of convenience consisted of 57 ACNPs assigned to various medical and surgical programs within acute care hospitals. Ten ACNPs participated in the unstructured qualitative interviews. In addition to the interviews, data pertinent to various organizational factors, including role formalization, receptivity of the role by others, perceived autonomy, role strain, and additional factors that may interfere with role implementation, were collected through a self-report structured questionnaire. A four-diary day was completed to gather data on role implementation. Descriptive and correlational statistics were used to analyze the quantitative data. The qualitative data were content analyzed. The ACNPs engaged most frequently in activities reflective of the clinical practice component of the role and less frequently in the non-clinical components (i.e., education, administration, and research). Results of the quantitative and qualitative analyses indicated that lack of formal clear job description, conflicting demands and expectations, lack of receptivity of the role by others, lack of autonomy, and increased workload were negatively correlated with the ACNP role implementation. The ACNP role implementation varies across practice settings. This variability should be accounted for when examining outcomes of ACNP care.

Acute Disease↗