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Biomedical subjects

P H Becker

Publications and source records attributed to P H Becker.

17 recordsLinked to original sources
PubMed2006

The contributions of age and sex to variation in common tern population growth rate.

1. The decomposition of population growth rate into contributions from different demographic rates has many applications, ranging from evolutionary biology to conservation and management. Demographic rates with low variance may be pivotal for population persistence, but variable rates can have a dramatic influence on population growth rate. 2. In this study, the mean and variance in population growth rate (lambda) is decomposed into contributions from different ages and demographic rates using prospective and retrospective matrix analyses for male and female components of an increasing common tern (Sterna hirundo) population. 3. Three main results emerged: (1) subadult return was highly influential in prospective and retrospective analyses; (2) different age-classes made different contributions to variation in lambda: older age classes consistently produced offspring whereas young adults performed well only in high quality years; and (3) demographic rate covariation explained a significant proportion of variation in both sexes. A large contribution to lambda did not imply a large contribution to its variation. 4. This decomposition strengthens the argument that the relationship between variation in demographic rates and variation in lambda is complex. Understanding this relationship and its consequences for population persistence and evolutionary change demands closer examination of the lives, and deaths, of the individuals within populations within species.

Aging↗
PubMed2000

Organochlorine and mercury contamination of little terns (Sterna albifrons) breeding at the western Baltic Sea, 1978-96.

Between 1978 and 1996, egg and chick samples of little terns (Sterna albifrons) breeding at different colony sites along the eastern coast of Schleswig-Holstein, Germany, were annually gathered by chance in the framework of a long-term ringing programme. Analyses of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), hexachlorobenzene (HCB), hexachlorocyclohexane (HCHs), and mercury were carried out on eggs, chicks, and down (only mercury). In all matrices, pollutant concentrations decreased over the 19-year period. The mixture compositions of Sigma PCB, Sigma DDT, and Sigma HCH changed during the previous decades indicating decreasing releases of PCB mixtures, DDT, and technical HCH mixtures. The pollutant concentrations currently found in the tern eggs are compared with those of other bird species from other Baltic Sea subregions, suggesting a relatively low pollution of the Belt Sea. The temporal trends in contamination are related to international measurements and conventions on bans of pollutants. Since individually known females were recaptured up to three times, inter-individual variation in pollutant burdens could be studied. Remarkable variation among individuals as well as between breeding seasons were found that were not explainable by general temporal trends. Influences of individually and seasonally varying feeding habits on this phenomenon are discussed. Compositions of individual PCB mixtures varied in relation to total PCB concentrations found in eggs suggesting a concentration-dependent metabolization of PCBs as with other species. Amounts of particular organochlorines varied between matrices possibly indicating metabolization of low chlorinated PCBs, beta-HCH, and HCB during embryogenesis. In mercury, body detoxification via down is assumed. As indicated by eggshell parameters (thickness and index) being not related to organochlorine concentrations and being similar to that found in historical studies, respectively, effects of recent organochlorine contamination on eggshell thickness seem to be improbable. In conclusion, influences of contamination on declining little tern stocks observed in Germany are discussed. Negative influences of contamination in the 1960s and 1970s are assumed to be probable.

Journal Article↗
PubMed1999

Bird blood as bioindicator for mercury in the environment.

Mercury concentrations were studied in blood, down and feathers of Common Gull (Larus canus L.) to investigate the suitability of bird blood as a matrix for biomonitoring of mercury in the marine environment. Chicks were collected in 1996 on the Elbe river and the Jade Bay. Like the side feathers, blood indicated site differences in mercury contamination. Correlational analyses showed that mercury concentrations in blood are significantly related to levels in side feathers (p < 0.001; Pearson), but not to those in down (p > 0.05; Pearson). Therefore, blood can be considered as a suitable matrix to indicate the current mercury burden in wild birds.

Animals↗
PubMed1996

Caring for self: becoming a self-reflective nurse.

Grounded in teaching experiences with nursing students, Dewey's educational philosophy, principles of adult learning, and phenomenologic perspectives, the article presents a model of self-reflection discovered in the educational/learning process of caring for self. Self-reflection as a process is operationalized as a bending back of attention and a focus on self to uncover silence and meanings or essences of personal and professional experience. Critical outcomes of this process are increased awareness, increased depth and breadth of understanding, and expanded consciousness. The thesis that self-reflection is a critical process in caring for others is presented. The background for the work and the nursing course where students develop a clinical experience of caring for self are discussed. The article includes graphic representations of the reflective process and proposes that, through caring for self, transformation in caring experiences is possible.

Adult↗
PubMed1994

Differences in mercury contamination and elimination during feather development in gull and tern broods.

Eggs, feathers (down, body feathers from side/shoulder and back) and some dead chicks (liver) from broods of three species, herring full (Larus argentatus), black-headed gull (Larus ridibundus), and common tern (Sterna hirundo) from the German North Sea coast were collected to study intersibling differences in mercury contamination and elimination into the growing feathers. The mercury contamination in eggs, feathers, and liver of the terns was about four times that of the gulls; black-headed gulls had lowest mercury concentrations. The body feathers grow when the chicks became older had lower mercury levels than down in the more contaminated species (11% lower in herring gulls, 49% in common terns), indicating the advancing decontamination of the body by the plumage development. The elimination of mercury was greater in chicks with higher mercury levels. Down of the first hatched herring gull and common tern chick contained more mercury than down of the siblings hatched later, because of its higher burden derived from the first laid egg.

Animals↗
PubMed1993

Mercury levels in eggs, tissues, and feathers of herring gulls Larus argentatus from the German Wadden Sea Coast.

The relationships between mercury levels in eggs, tissues, and feathers of male and female herring gulls caught at their nests at a colony on the German Wadden Sea Coast were investigated, and an assessment of mercury intake and excretion of these birds was made. Samples of the liver, ovary, pectoral muscle, and body feathers, as well as the primary feather (in some cases), and eggs were taken from 37 adult herring gulls. Analysis of total mercury in all samples showed that body-feather and tissue levels were independent of sex. There was, however, a significant difference between levels of mercury in the primary feathers of male and female birds. Egg levels were not correlated to pectoral muscle, ovary, or feather levels although they were positively correlated with mercury levels in the liver. Liver levels were in turn correlated with mercury levels in the ovary. The ratio of mean feather to mean egg concentration ranged from 3.7 to 5.5 according to which feather was used. It was estimated that herring gulls from the Wadden coast ingested between 825 and 1337 microg of mercury in the year prior to analysis. It was also estimated that female birds may excrete over 20% more mercury via their eggs than could be excreted by male birds.

Journal Article↗
PubMed1993

Hatching failure in common terns (Sterna hirundo) in relation to environmental chemicals.

The hatching success of two Common Tern colonies, a highly contaminated one at the Elbe estuary (Hullen) and a less contaminated one at the Jade (Augustgroden, southern North Sea coast, Germany), was similar in 1988; 69% at Hullen and 73% at Augustgroden. Most egg loss was due to predators. The number of eggs failing to hatch from unknown causes was 6.3% higher at Hullen than at Augustgroden. Egg-shell thickness and strength were not correlated with the chemicals' concentrations. At Hullen unhatched eggs were compared with randomly collected fresh eggs; the former containing a significantly higher amount (20%) of PCBs (134 microg) than the eggs collected at random (112 microg). Seven out of 45 PCB-congeners were found in significantly higher amounts in the failed eggs, among them the toxic congener PCB 138. The two samples showed no difference in mercury concentration, which was 6.2 mg kg(-1), nor difference in shell strength. Eggs of Common Terns breeding at the Elbe estuary had concentrations of some contaminants reaching levels endangering breeding success.

Journal Article↗
PubMed1991

Guidance for selecting nuclear instrumentation derived from experience in the Goiânia accident.

Selecting equipment to be used in emergencies is not a simple task. In the radiological accident that occurred in Goiânia, a large variety of instruments from different manufacturers were used, and we observed some of their limitations and advantages. This work presents, in a condensed form, the major problems that occurred with the equipment used in Goiânia and practical observations that could be helpful for instrument selection.

Accidents↗
PubMed1987

'Pseudonormalisation' of the 'normal variant pattern' on the ECG of black subjects after intermittent acute myocardial ischaemia. A case report.

A middle-aged urbanised black man with unstable angina pectoris showed unusual findings on serial resting ECGs recorded during episodes of chest pain, as well as during symptom-free intervals. The 'normal variant pattern', known to occur in blacks, was recorded in the absence of angina; in a white patient with chest pain it would have been considered as being due to a possible hyperacute myocardial infarction. During repeated episodes of severe angina, 'pseudonormalisation' of the 'normal variant pattern' was seen but the pointer to myocardial ischaemia was the simultaneous occurrence of ST-segment depression, Selective coronary arteriography delineated critical lesions in both the left anterior descending and dominant left circumflex coronary arteries. Coronary artery bypass surgery was successful. The importance of recognition of the 'normal variant pattern' in the black population in which the incidence of atherosclerotic coronary artery disease is rising, is emphasised.

Black or African American↗
PubMed1986

Angina pectoris and acute myocardial infarction due to "slow-flow phenomenon" in nonatherosclerotic coronary arteries: a case report.

A 51 year-old White woman with angina pectoris and nonatheromatous coronary artery disease is presented. Cardiac catheterization demonstrated a "slow-flow phenomenon" in the left coronary artery accompanied by severe angina pectoris and anterolateral ST-segment elevation and culminating in an acute nontransmural myocardial infarction. At repeat coronary arteriography, ergonovine maleate provocation proved negative. This patient is unique, since the previously documented 6 cases with this coronary cineangiographic response did not exhibit angina pectoris or ECG evidence of myocardial ischemia during the "slow-flow phenomenon," and none was complicated by an acute myocardial infarction. Various aspects of the pathophysiology of angina pectoris in this patient, including the recently described "reduced vasodilator reserve" concept, are briefly outlined.

Angina Pectoris↗
PubMedDate not supplied

A program evaluation approach to drug administration education.

To evaluate the education of undergraduate nursing students in drug administration, the faculty of La Salle University School of Nursing structured a program evaluation plan using a curriculum map. Faculty track the cognitive, affective, and psychomotor skills involved in drug administration. For example, all clinical nursing courses and the pharmacology course contain dosage and intravenous solution calculations in didactic material and tests. Program evaluation of the outcomes of medication administration education is continuous throughout the curriculum.

Curriculum↗