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Biomedical subjects

D Keller

Publications and source records attributed to D Keller.

At least 19 recordsLinked to original sources
PubMed1994

Safety and immunogenicity of a recombinant outer surface protein A Lyme vaccine.

OBJECTIVE: To evaluate the safety and immunogenicity of a recombinant outer surface lipoprotein A (OspA) Lyme vaccine in healthy adults. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Clinical research unit of a medical center. PARTICIPANTS: Thirty-six healthy adult volunteers aged 18 through 65 years. INTERVENTIONS: Volunteers were randomly assigned to receive two 10-micrograms doses of OspA Lyme vaccine, OspA Lyme vaccine adsorbed to alum, or a buffer placebo. Subjects in the OspA Lyme vaccine group received a third dose. Patients were assessed after each vaccination for a total follow-up period of 1 year. Serum samples for antibody determination were drawn at baseline, 2 and 3 weeks after dose 1, once per week for 4 weeks after dose 2, 20 weeks after dose 2, and 1 month after dose 3. MAIN OUTCOME MEASURES: Local and systemic adverse reactions and antibody levels specific for OspA. RESULTS: The most common reactions were local pain and tenderness at the injection site. Adverse events did not increase following the second or third dose. Two doses of both vaccine formulations elicited high-titer antibodies that inhibited replication of Borrelia burgdorferi in vitro. No differences were noted in antibody levels elicited by the adsorbed and nonadsorbed formulations. CONCLUSION: Two or three doses of OspA Lyme vaccine are safe and immunogenic in adults.

Adolescent↗
PubMed1993

Comparative effects of in vivo treatment using interleukin-11 and stem cell factor on reconstitution in mice after bone marrow transplantation.

Molecular analysis of the hematopoietic microenvironment (HM) has led to the characterization and molecular cloning of two unique growth factors produced by stromal cells. Interleukin (IL)-11 and stem-cell factor (SCF; steel factor [SF]) have been shown in a variety of in vitro culture systems to stimulate distinct populations of stem, progenitor, and more differentiated cell types. We have analyzed and compared the effects of each growth factor administered to mice undergoing bone marrow transplantation (BMT) after total body irradiation (TBI). We report that IL-11 stimulates platelet and neutrophil recovery, while the main effect of SCF is on erythroid cell recovery in this model. Mice treated with the combination of IL-11 and SCF show increases in all three lineages compared with control mice, without obvious toxicity. In addition, both the type of progenitor- and stem-cell populations stimulated and the anatomic localization of effects seen with each growth factor are distinct. These data in mice suggest that the combination of IL-11 and SCF might be useful in humans undergoing myeloablative therapies.

Animals↗
PubMed1993

Cytoskeleton of living, unstained cells imaged by scanning force microscopy.

Subsurface cytoskeletal structure can be visualized in either fixed or living mammalian cells in aqueous medium with approximately 50 nm resolution using the Scanning Force Microscope (SFM). In living cells, changes in cell topography, or subsurface cytoskeleton caused by the introduction of drugs (colchicine) or cross-linking of surface receptors (by antibodies against IgE bound to the IgE receptor) can be followed in time. Contrast in SFM images of cell surfaces result from both topographic features of the cell and from variations in cell surface "stiffness". The SFM is therefore capable of measuring local compliance and stress in living cells, and so should make it possible to map the cytoskeletal forces used to generate cell motions and changes in cell shape.

Animals↗
PubMed1993

Retreating orthodontic failures: Part I.

This article presents a number of cases originally treated by orthodontic specialists which were retreated because the initial results became unstable over time. Diagnostic evaluations uncovered many common reasons for the initial treatment failures. Methods utilized during re-treatment addressed the causative factors related to the initial instability and have proven effective in maintaining a consistent dental relationship for over five years. The results have been both aesthetic and functional.

Humans↗
PubMed1993

Retreating orthodontic failures: Part II.

Part I of this series (June 1993 JGO) clearly documented the inadequacies of some orthodontic methods to obtain satisfactory stable results for patients. Forty-four patients were selected for this study, as their prior orthodontic treatments--all from orthodontic specialists or orthodontic postgraduate institutions--had failed for a variety of functional reasons. The treatment for the 44 patients would not have been necessary if the initial orthodontic treatment had been successful. Therefore, somewhere in the treatment, problems existed which were not corrected by the treatment methods, or problems arose because of the treatment methods. Part I of this series clearly and precisely showed that some orthodontic methods initiate TMJ problems. In a review of the literature presented in Part I, the following conclusions were reached: 1. The optimum functional relationship of the human temporomandibular joint exists when the force vectors within the joint are directed anteriorly and superiorly. 2. Some orthodontic treatments disrupt this optimum functional relationship by placing posterior or posterior/superior forces on the structures of the temporomandibular joint. 3. There is an increased incidence of joint signs and symptoms for some of the patients treated with those conventional methods which place pathologic forces on the temporomandibular joints. Present treatment methods are inadequate if they damage the patient's structures. The guidelines of treatment are wrong if problems exist because of the treatment methods and these guidelines then need to be corrected. What is offered in this article is a method of treatment that was and is successful in retreating those patients who were initially treated by orthodontic specialists, yet who developed TMJD problems during or after their treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Occlusion, Centric↗
PubMed1992

Substrate preparation for reliable imaging of DNA molecules with the scanning force microscope.

A simple method of substrate preparation for imaging circular DNA molecules with the scanning force microscope (SFM) is presented. These biomolecules are adsorbed onto mica that has been soaked in magnesium acetate, sonicated and glow-discharged. The stylus-sample forces that may be endured before sample damage occurs depends on the ambient relative humidity. Images of circular DNA molecules have been obtained routinely using tips specially modified by an electron beam with a radius of curvature, Rc, of about 10 nm [D. Keller and C. Chih-Chung, Surf. Sci. 268 (1992) 333]. The resolution of these adsorbed biomolecules is determined by the Rc. At higher forces individual circular DNA molecules can be manipulated with the SFM stylus. Strategies to develop still sharper probes will be discussed.

Aluminum Silicates↗
PubMed1991

Relative and combined effects of heat and noise exposure on sleep in humans.

In a counter-balanced design, the effects of daytime and/or nighttime exposure to heat and/or traffic noise on night sleep were studied in eight healthy young men. During the day, the subjects were exposed to baseline condition (ambient temperature = 20 degrees C; no noise) or to both heat (35 degrees C) and noise. The duration of the daytime exposure was 8 h ending 5 h before sleep onset. The following nights, the subjects slept either in undisturbed (20 degrees C; no noise) or in noise, heat, or noise plus heat-disturbed environments. During the day, the various types of traffic noise were distributed at a rate of 48/h with peak intensities ranging between 79 and 86 dB(A). The background noise level was at 45 dB(A). At night, the peak intensities were reduced by 15 dB(A), the rate was diminished to 9/h, and the background noise was at 30 dB(A). Electrophysiological measures of sleep and esophageal and mean skin temperatures were continuously recorded. The results showed that both objective and subjective measures of sleep were more disturbed by heat than by noise. The thermal load had a larger impact on sleep quality than on sleep architecture. In the nocturnal hot condition, total sleep time decreased while duration of wakefulness, number of sleep stage changes, stage 1 episodes, number of awakenings, and transitions toward waking increased. An increase in the frequency of transient activation phases was also found in slow-wave sleep and in stage 2. In the nocturnal noise condition, only total number of sleep stage changes, changes to waking, and number of stage 1 episodes increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Human IgE-binding protein: a soluble lectin exhibiting a highly conserved interspecies sequence and differential recognition of IgE glycoforms.

IgE-binding protein (epsilon BP) refers to a protein originally identified in rat basophilic leukemia cells by virtue of its affinity for IgE. It is now known to be a beta-galactoside-binding lectin equivalent to carbohydrate-binding protein 35 (CBP 35). More recently, its identity to Mac-2, a macrophage cell-surface protein, has been established. cDNA coding for human epsilon BP has been cloned from a human HeLa cell cDNA library and contains an open reading frame of 750 base pairs encoding a 250 amino acid protein. Like the rat and murine counterparts, the human epsilon BP amino acid sequence can be divided into two domains with the amino-terminal domain consisting of a highly conserved repetitive sequence (YPGXXXPGA) and the carboxyl-terminal domain containing sequences shared by other S-type lectins. The human epsilon BP sequence exhibits extensive homology to murine and rat epsilon BP with 84% and 82% identity, respectively. The homology is particularly striking in the carboxyl-terminal domain where 95% identity is found between human and murine sequences in a stretch of over 70 amino acids. A survey of epsilon BP mRNA expression from several lymphocyte cell lines revealed that the level of epsilon BP transcription may reflect a relationship between cell differentiation and epsilon BP expression. Finally, human epsilon BP was purified from several human cell lines and shown to possess lactose-binding characteristics and cross-species reactivity to murine IgE. Surprisingly, three different human myeloma IgE proteins did not show reactivity to human epsilon BP. However, after neuraminidase treatment of each human IgE, pronounced binding to epsilon BP was observed, thereby indicating that only specific IgE glycoforms can be recognized by epsilon BP.

Amino Acid Sequence↗
PubMed1989

Imaging of metal-coated biological samples by scanning tunneling microscopy.

A method for imaging biological samples by scanning tunneling microscopy (STM) is presented. There are two main difficulties in imaging biological samples by STM: (1) the low conductivity of biological material and (2) finding a method of reliably depositing the sample on a flat conducting surface. The first of these difficulties was solved by coating the samples with a thin film of platinum-carbon. The deposition problem was solved by a method similar to a procedure used to deposit biological molecules onto field ion microscope (FIM) tips. STM images of bacteriophage T7 and filamentous phage fd are shown. The substrate on which the samples were absorbed was atomically flat gold. The images do not show molecular detail due to the metal coating, but the gross dimensions and morphology are correct for each type of virus. Also, the surface density of virus particles increases and decreases in the way expected when the conditions of deposition are changed. These methods allow reliable and reproducible STM imaging of biological samples.

Bacteriophages↗
PubMed1989

Imaging of single uncoated DNA molecules by scanning tunneling microscopy.

Scanning tunneling microscope images of DNA molecules absorbed onto highly oriented pyrolytic graphite have been obtained. Three methods of deposition and sample preparation have been utilized. In the first method, a highly concentrated solution of DNA is sonicated, and a drop is deposited on freshly cleaved graphite. Under these conditions, the molecules tend to align in a parallel fashion, forming liquid-crystalline phases. In the second method, a solution of DNA is deposited directly on the graphite surface without sonication. In this case, ammonium acetate, a volatile salt, is used to decrease the amount of the residual salt crystals left after drying. In the third method, a solution containing lysed phage particles and DNA is adsorbed onto a graphite surface. The molecules are seen either isolated or in small bundles. The values of height, periodicity, and thickness observed and the handedness of the molecules are consistent with those expected for DNA. In all cases, the molecules were identified by their characteristic periodic structure and because, at higher magnification, no graphite-like structure was detectable on the surface of the molecules. Often the DNA molecules appear to adsorb in areas of the graphite that have many steps and defects. A mechanism that explains the magnitude of the tunneling currents measured in DNA is proposed. This mechanism, in turn, suggests a general method by which large insulating molecules can be rendered conductive.

DNA↗
PubMed1987

Differential polarization imaging. I. Theory.

A theory of differential polarization imaging is derived using Mueller calculus. It is shown that, for any arbitrary object, 16 images (in general different) can be obtained by combining different incident polarizations of light and measuring the specific polarization components transmitted or scattered by the object. These are called the Mueller images of the object. Mathematical expressions of these images for an object of arbitrary geometry are derived using classical vector diffraction theory and the paraxial and thin lens approximations. The object is described as a collection of point polarizable groups. The electromagnetic fields are calculated using the first Born-Approximation, but extension of the theory to higher-order approximations is shown to be straightforward. These expressions are obtained for the transmission, or bright-field, geometry, and the scattering, or dark-field, configuration. In both cases, the contributions of scattering, absorption, and background illumination to the Mueller images are characterized. The contributions of linear dichroism, circular dichroism, and linear and circular intensity differential scattering to certain Mueller images are established. It is shown that the Mueller images represent a complete two-dimensional mapping of the molecular anisotropy of the object.

Mathematics↗
PubMed1986

Laboratory procedures in adenoviruses. XII. Comparison of five ELISA methods for demonstration of hexon antigen.

To demonstrate adenovirus hexon, four different arrangements of a four-layer ELISA, to be performed with commercially available reagents, were compared with a three-layer ELISA. After evaluation of specific and control reagents and their dilutions, the guinea pig/rabbit or the rabbit/chicken method were equally practicable and sensitive as the three-layer method with rabbit serum and superior to two other methods. By testing about 100 stool samples and 74 throat swabs containing adenoviruses, it turned out that the sensitivity (1 ng/ml hexon) appears satisfactory for stool specimens in adenovirus enteritis of infants, but is much less sensitive than isolation in cell culture for adenoviruses in throat swabs. As confirmatory test, specimen were incubated with an adenovirus rabbit antiserum or normal serum and then tested.

Adenoviridae Infections↗
PubMed1986

Validation of the Functional Assessment Inventory against a multidisciplinary home care team.

Systematic multidimensional assessment techniques such as the Functional Assessment Inventory (FAI) are increasingly used with the elderly for outcome measurement, prediction of service needs, and accurate description for comparative purposes. The FAI is a structured interview followed by a rating process which compares patient status against standard descriptive phrases. Patients are assessed in five areas: mental health, physical health, social resources, economic resources, and activities of daily living (ADL). The validity of the FAI was tested by comparing ratings of patient health obtained by a single investigator using only the instrument with ratings obtained by consensus from an interdisciplinary home care team providing long-term care for the patients studied. An excellent level of agreement (weighted kappas from .583 to .780) was found in all areas studied. A single significant difference in ADL rating with a high correlation coefficient (r = .85) was interpreted as due to a difference between the single rater and the team in the definition of ADL. The ease of obtaining summary ratings from clinical personnel suggests that further exploration of this rapid quantification of patient health is warranted.

Activities of Daily Living↗
PubMed1985

[New viewpoints on the prognostic index in malignant melanomas].

Investigation of anamnestic development, Tumor types, levels of invasion (Clark), tumor thickness (Breslow), mitotic index (Schmoeckel and Braun-Falco) in 407 (without lentigo maligna and preinvasive superficial spreading melanoma 317) cases revealed an interdependence between thickness and mitotic index. This is a theoretical argument against the "prognostic index" as a product of both these parameters.

Humans↗
PubMed1985

Imaging of optically active biological structures by use of circularly polarized light.

If an optically active (chiral) sample is placed in a microscope and illuminated with circularly polarized light, an image can be formed that is related to the circular dichroism of each feature of the sample. A theoretical investigation has been done for the circular differential image obtained by subtracting the images formed under right- and left-circularly polarized light. Two types of differential images are possible: (i) dark-field images formed from light reflected or scattered by the sample and (ii) bright-field images formed from light transmitted through the sample. The sign and magnitude of each feature in a circular differential image strongly depend on the structure of the sample. The dark-field circular differential images are most sensitive to large features with dimensions similar to the wavelength of illumination whereas the bright-field images are most sensitive to the short-range molecular order. Applications of circular differential imaging may include clinical fingerprinting of normal and transformed cells and structural analysis of individual cellular components.

Circular Dichroism↗