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Biomedical subjects

L Keller

Publications and source records attributed to L Keller.

At least 55 records · Page 3Linked to original sources
PubMed1995

X-ray powder diffraction patterns of calcium phosphates analyzed by the Rietveld method.

Least-square refinement of x-ray powder diffraction patterns analyzed by the Rietveld method can yield structural information which had been unattainable or at least elaborate to obtain by conventional pattern analysis. The Rietveld method calculates a powder pattern on the basis of a structural model as well as the characteristics of the instrument used, and minimizes the differences between the intensities observed and the intensities calculated. The method is applied on patterns produced powders or polycrystalline solids on conventional powder diffractometers. For materials containing more than one crystalline phase with known structures such as hydroxyapatite (HA) and whitlockite (beta-TCP), pattern analysis yields phase quantification without internal or external standards. Refinement of the lattice parameters a0 and c0 determines the degree of dehydroxylation in plasma-sprayed HA coatings. The presence of amorphous Ca phosphates in HA coatings is detected by background modeling. The calculation of entire powder patterns allows discrimination of small concentrations of poorly crystallized Ca phosphate phases against the background, and prevents gross aberrations in estimating secondary phases. Even detect structures such as an OH-deficient HA lattice can be detected through slight differences in diffracted intensity by which the pattern calculated deviates from the pattern observed.

Biocompatible Materials↗
PubMed1994

[Prognostic evaluation of patients with arteriosclerosis obliterans].

The natural course of 365 random patients with peripheral arterial obliterative disease was followed up on an average 8 years. In 36% of the patients worsening of angiological condition has been shown. The state of the other patients was unchanged (55%) or improved (9%). During the observation period 87 angiological surgeries and amputation of 41 lower limbs were performed, most of them in 1-2 years after onset of the disease. At follow up in 151 cases myocardial infarction and in 72 cases stroke occurred; the incidence of both diseases was characterized by a cluster like accumulation in 1-3 years before or after onset of the disease. The deterioration of the angiological condition of the patients was related to smoking (mainly heavy smoking), diabetes mellitus and-even more markedly--to the combinations of different risk factors including smoking. The pathological levels of haemorheological factors also showed significant connection with the severity of the disease. In the prospective 6 year period of the study 147 patients (40%) died. This mortality was twice that of the general population matched for age and sex. Information about the cause of death could be collected in 128 cases (87%), among them 51 (40%) died of vascular diseases (peripheral arterial obliterative disease, myocardial infarction, stroke).

Aged↗
PubMed1993

[Relation of angiographic changes to clinical data and risk factors in patients with arteriosclerosis obliterans].

The arteriographical changes of 66 patients with peripheral arterial obliterative disease and the relationship between the observed alterations and certain clinical and laboratory data as well as some risk factors were analysed. A score system was used to quantify the arteriosclerotic lesions. The arterial alterations of the examined 90 extremities were studied in the pelvic (common and external iliac arteries), femoral (common, superficial, deep femoral and popliteal arteries) and crural (anterior and posterior tibial arteries) regions. Pathomorphological changes in 433 of the investigated 720 arteries were shown, from among them plaque in 11.8%, stenosis in 22.3%, total occlusion in 26% were proved. Most frequently (89%) the superficial femoral artery was affected. As to the single vessels, the superficial femoral and posterior tibial arteries, while among the zones the femoral region proved to be most serious radiologically. The degree and extent of vessel lesions were related to age. The morphological severity was basically concordant with the results of clinical investigations (walking distance, ergometry, Doppler index). The separately examined risk factors (smoking, hypertension, diabetes, hypercholesterolemia, hypertriglyceridemia) were not related consequently to the radiological changes, but in certain combinations, as heavy smoking with hypertension and heavy smoking with diabetes, the relationship proved to be statistically significant.

Adult↗
PubMed1993

Effect of a founder event on variation in the genetic sex-determining system of the fire ant Solenopsis invicta.

Effects of a recent founder event on genetic diversity in wild populations of the fire ant Solenopsis invicta were studied, with particular attention given to the genetic sex-determining system. Diploid males are far more common relative to haploid males in introduced populations than in native populations of fire ants, and queens that produce diploid males account for a significantly larger proportion of the mated queens in introduced than in native populations. Differences between native and introduced populations in attributes of the mating systems (i.e., queen mating frequency or level of inbreeding) can be excluded as factors contributing to these different levels of diploid male production. Thus, we conclude that diploid males have increased in frequency in introduced populations because of a loss of allelic diversity at the sex-determining locus (loci). This loss of sex alleles has generated a substantial increase in the estimated segregational genetic load associated with production of sterile diploid males in introduced populations over the load in native populations. The loss of allelic diversity in the sex-determining system in introduced S. invicta is paralleled by a loss of electrophoretically detectable rare alleles at protein-encoding loci. Such concordance between these different types of markers is predicted because each of the many sex alleles present in the native populations is expected to be rare. Estimates of expected heterozygosity (Hexp) based on 76 electrophoretic loci do not differ significantly between the native and introduced fire ant populations, illustrating the lack of sensitivity of this measure for detecting many types of bottlenecks.

Alleles↗
PubMed1992

Elastase-type enzymes and their relation to blood lipids in atherosclerotic patients.

Serum elastase-type activity, elastase inhibitory capacity and their relation to lipids were examined in 140 male patients with ischemic vascular disease (coronary, cerebral, peripheral) and in 60 control subjects. In a further 24 patients with acute myocardial infarction elastase activity, inhibitory capacity and lipids during the course of the illness have also been investigated. Serum elastase-type activity was found to be significantly lower and inhibitory capacity significantly higher in the groups of patients than in the controls. HDL- and HDL2-cholesterol as well as apo A concentration showed significant negative correlation with elastase inhibitory capacity both in atherosclerotic and in control subjects. During the course of myocardial infarction a significant elevation of serum elastase-type activity could be observed at the end of the first week; serum triglyceride levels increased, HDL- and HDL2-concentrations decreased significantly in the first 3 weeks, than gradually approached the initial values. In the patients with an elevation of serum elastase-like activity by more than 30% in the first week, there was a significantly higher elevation of serum GOT and LDH1 and a greater occurrence of transmural (Q) infarction than in those with a smaller variation of elastase-like activity.

Adult↗
PubMed1992

A training project helps the poor. A rural healthcare facility offers job training, gains employees.

As poor Americans look for work, healthcare facilities face a shortage of workers. One facility, Saint Francis Medical Center in Grand Island, NE, found a way to help some of the area's financially disadvantaged persons receive technical training and employment as it eased its own personnel shortage. Saint Francis leaders assembled a team of representatives from the hospital's staff, the Greater Nebraska Job Training Program, Lincoln, and Central Community College, Grand Island, to establish the Rural Allied Medical Business Occupations program. The team reviewed several job descriptions to help it decide which jobs to include in the program and surveyed area hospitals to ensure the positions selected were experiencing shortages. The program received a grant as a demonstration project from the U.S. Department of Education. After identifying participants who had the aptitudes and interests for the jobs, the Rural Medical Allied Medical Business Occupations program arranged for participants' training and assistance with items such as tuition, child care, and transportation. Participants received training at Central Community College and at Saint Francis Hospital. Saint Francis Medical Center deemed the program a success. The hospital has hired seven healthcare workers who would not have been available if they had not been trained through this program. Moreover, the program provides yet another way for the hospital to help fulfill a major portion of its mission: to help the poor.

Allied Health Occupations↗
PubMed1991

[Serum elastinolytic activity and blood lipids in various clinical forms of arteriosclerosis and in acute myocardial infarct].

Serum elastase-type activity, elastase inhibitory capacity and their relation to lipids were examined in 140 male patients with ischemic vascular disease (coronary, cerebral, peripheral) and in 60 control subjects. In further 24 patients with acute myocardial infarction dynamics of elastase activity, inhibitory capacity and of lipids during the course of the illness have also been investigated. Serum elastase-type activity was found to be significantly lower, inhibitory capacity significantly higher in the groups of patients than in the controls. HDL- and HDL2 cholesterol and apo-A concentrations showed significant negative correlations with elastase inhibitory capacity both in atherosclerotic and in control subjects. During the course of myocardial infarction a significant elevation of serum elastase-type activity could be observed at the end of the first week; serum triglyceride levels increased, HDL- and HDL2 concentrations decreased significantly in the first 3 weeks, then gradually approached the initial values. In the subgroup of patients with an elevation of serum elastase-like activity by more than 30% in the first week, there was a significantly higher elevation of serum GOT and LDH1 and a greater occurrence of transmural (Q) infarction than in those with a smaller variation of elastase-like activity.

Arteriosclerosis↗
PubMed1991

A quantitative approach to the characterization of cumulative and average solvent exposure in paint manufacturing plants.

Previous reports have attributed a range of neurobehavioral effects to low-level, occupational solvent exposure. These studies have generally been limited in their exposure assessments and have specifically lacked good estimates of exposure intensity. In the present study, the authors describe the development of two exposure variables that quantitatively integrate industrial hygiene sampling data with estimates of exposure duration--a cumulative exposure (CE) estimate and a lifetime weighted average exposure (LWAE) estimate. Detailed occupational histories were obtained from 187 workers at two paint manufacturing plants. Historic industrial hygiene sampling data for total hydrocarbons (a composite variable of the major neurotoxic solvents present) were grouped according to 20 uniform, temporally stable exposure zones, which had been defined during plant walk-through surveys. Sampling at the time of the study was used to characterize the few zones for which historic data were limited or unavailable. For each participant, the geometric mean total hydrocarbon level for each exposure zone worked in was multiplied by the duration of employment in that zone; the resulting products were summed over the working lifetime to create the CE variable. The CE variable was divided by the total duration of employment in solvent-exposed jobs to create the LWAE variable. The explanatory value of each participant's LWAE estimate in the regression of simple visual reaction time (a neurobehavioral test previously shown to be affected by chronic solvent exposure) on exposure was compared with that of several other exposure variables, including exposure duration and an exposure variable based on an ordinal ranking of the exposure zones.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical Industry↗
PubMed1991

Serum elastase-type enzymes and their correlation to blood lipids in male patients with atherosclerosis.

Serum elastase-type activity, elastase inhibitory capacity and their relation to lipids were examined in 140 male patients with ischaemic vascular disease (coronary, cerebral, peripheral) and in 60 control subjects. Serum elastase-type activity was found to be significantly lower, inhibitory capacity significantly higher, in the groups of patients than in the controls. HDL- and HDL2 cholesterol as well as apo A concentration showed significant negative correlation with elastase inhibitory capacity both in atherosclerotic and in control subjects.

Apolipoproteins A↗
PubMed1989

Eimeria tenella and E. acervulina: lymphokines secreted by an avian T cell lymphoma or by sporozoite-stimulated immune T lymphocytes protect chickens against avian coccidiosis.

The role of avian lymphokines as nonspecific immunomodulators of host immunity against the intracellular parasite Eimeria was investigated. Prophylactic treatment of normal chickens with crude cell-free supernatants obtained from JMV-1 culture, concanavalin A (Con A)-stimulated normal spleen cells, or sporozoite-stimulated immune T cells prior to inoculation with E. tenella or E. acervulina conferred significant protection. These crude cell-free culture supernatants also inhibited intracellular development of eimerian parasites in vitro. Avian macrophages pretreated with these supernatant preparations showed inhibitory activity against Eimeria. This inhibitory activity could not be ascribed to anti-Eimeria antibody, complement, or cell-free Marek's disease virus and was therefore considered to be due to immunomodulating lymphokines present in the culture supernatants. These results suggest that JMV-1-transformed T lymphoblastoid cells, immune T lymphocytes, and Con A-stimulated normal spleen cells secrete lymphokines that can enhance host immunity in a nonspecific manner and implicate cell-mediated immunity as a major mechanism of the protective host immune response against eimerian infections.

Animals↗
PubMed1989

Methods for the reduction of AIDS social anxiety and social stigma.

A cognitive-social model is proposed for the study of AIDS social attitudes. Features of the ambivalent (fear and compassion) public belief system toward PWAs are outlined and ways to increase altruism and reduce fear are specified. Three studies are reported using cognitive-social methods for the reduction of AIDS social anxiety and social stigma. Study 1 found that cognitive inoculation and abbreviated group desensitization equally reduced AIDS social anxiety measured by a verbal scale. One form of brief group desensitization was superior to basic factual, counterphobic inoculation in reducing desire for social restriction of persons with AIDS (PWAs). In Study 2 subject improvisational role playing of PWAs increased positive attitudes toward PWAs and desire for altruistic actions but did not reduce measured fear. Knowledge of AIDS was negatively correlated with AIDS social anxiety and desire for patient restriction. AIDS social anxiety was negatively correlated with altruism and positively correlated with homophobia. In Study 3, three forms of experimenter-guided mastery imagery reduced AIDS social anxiety and increased AIDS altruism. Results of these studies may have relevance to reducing high-risk contagious behavior, as well as to reducing AIDS social stigma and social anxiety. A componential model of AIDS education is described.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Glycosylation and secretion of acid phosphatase in Schizosaccharomyces pombe.

We have purified secreted acid phosphatase of Schizosaccharomyces pombe. The enzyme is N-glycosylated, the associated carbohydrate accounts for 90% of the total molecular mass and the protein moiety has a molecular mass of 54 kDa. The deglycosylated enzyme still exhibits enzymatic activity. Using antibodies recognizing the protein moiety of the enzyme we have identified two intracellular precursors of acid phosphatase: an unglycosylated membrane-bound 54-kDa form that accumulates in the presence of tunicamycin and a partially glycosylated 72-kDa form that accumulates mostly in membranes of cells grown in rich medium. We further showed that the conversion of the 54-kDa and 72-kDa forms to partially glycosylated and fully glycosylated acid phosphatase is a regulated process. Growth conditions determine how much of translated 54-kDa acid phosphatase is glycosylated to the 72-kDa form and how much remains unglycosylated in membranes. When cells are grown in a rich medium, 5% of the total acid phosphatase protein remains as unglycosylated enzyme and 8% as partially glycosylated 72-kDa form. In cells grown in the minimal medium, however, all of the 54-kDa and 72-kDa forms of acid phosphatase are rapidly processed to fully glycosylated enzyme. The 72-kDa form and the unglycosylated form of acid phosphatase are not secreted or transported to the plasma membrane.

Acid Phosphatase↗