Biomedical subjects

P Schultz

Publications and source records attributed to P Schultz.

At least 37 records · Page 2Linked to original sources

PubMed2000

[Secondary hypertrophic osteoarthropathy in a patient with pulmonary carcinoma].

BACKGROUND: Hypertrophic osteoarthropathy (HOA) is a syndrome that manifests itself by clubbing of fingers, periosteal and osteal neoformation in acral bones and oligo- or polysynovitis. It may occur as primary form (mostly hereditary) or secondary form, associated with various diseases, especially neoplastic or infectious diseases. PURPOSE: The purpose of the study was to point out that when the symptoms of HOA occur, it is necessary to search for the primary disease, which is usually represented by tumor. METHODS: The study reports a case of a patient with symptoms of HOA, pulmonary adenocarcinoma confirmed by histological examination, and with metastases spread into peripheral lymph nodes. The examination of symptomatology of HOA indicated that to pulmonary carcinoma. RESULTS: The medical history of the patient shows that if there is, at an early stage, little attention paid to the fact that HOA represents a paraneoplastic syndrome, cancer is then confirmed later at a more advanced stage. Neglection of this fact delays the primary diagnosis, deteriorates the prognosis and limits the treatment by the extent of the cancerous process. CONCLUSION: In practice, manifestations of HOA may point to the primary cancerous disease. When the symptomatology of HOA appears, radiograms usually pick up tumours at their early stages, which is important for the prognosis and the strategy of their treatment. The situation was different with the case reported in the study, because the disease was diagnosed at a more advanced stage, which unfavourably affected the prognosis and the treatment of the disease. (Tab. 1, Fig. 4, Ref. 15.)

Adenocarcinoma↗

PubMed2000

Indicators of intimate partner violence in women's employment: implications for workplace action.

The study examined the indicators and consequences of intimate partner violence on women's employment and associated types and levels of violence. Interviews were conducted with a consecutive sample of 90 women seeking a protective order. Actual and threatened violence was measured with the Severity of Violence Against Women Scales (46 items). Eight questions were asked about type of harassment experienced at the worksite. The results found most of the abused women had been employed at one time (87%) and had also experienced harassment from an intimate partner related to their work (89%). Findings indicated lost productivity and reduced performance. The researchers concluded poor work performance, tardiness, and absenteeism may indicate an employee is suffering from intimate partner violence.

Absenteeism↗

PubMed1999

Three-dimensional structures of the TAFII-containing complexes TFIID and TFTC.

TBP (TATA-binding protein)-associated factors (TAF(II)s) are components of large multiprotein complexes such as TFIID, TFTC, STAGA, PCAF/GCN5, and SAGA, which play a key role in the regulation of gene expression by RNA polymerase II. The structures of TFIID and TFTC have been determined at 3.5-nanometer resolution by electron microscopy and digital image analysis of single particles. Human TFIID resembles a macromolecular clamp that contains four globular domains organized around a solvent-accessible groove of a size suitable to bind DNA. TFTC is larger and contains five domains, four of which are similar to TFIID.

DNA-Binding Proteins↗

PubMed1999

Properties of polyglutamine expansion in vitro and in a cellular model for Huntington's disease.

Eight neurodegenerative diseases have been shown to be caused by the expansion of a polyglutamine stretch in specific target proteins that lead to a gain in toxic property. Most of these diseases have some features in common. A pathological threshold of 35-40 glutamine residues is observed in five of the diseases. The mutated proteins (or a polyglutamine-containing subfragment) form ubiquitinated aggregates in neurons of patients or mouse models, in most cases within the nucleus. We summarize the properties of a monoclonal antibody that recognizes specifically, in a Western blot, polyglutamine stretches longer than 35 glutamine residues with an affinity that increases with polyglutamine length. This indicates that the pathological threshold observed in five diseases corresponds to a conformational change creating a pathological epitope, most probably involved in the aggregation property of the carrier protein. We also show that a fragment of a normal protein carrying 38 glutamine residues is able to aggregate into regular fibrils in vitro. Finally, we present a cellular model in which the induced expression of a mutated full-length huntingtin protein leads to the formation of nuclear inclusions that share many characteristics with those observed in patients: those inclusions are ubiquitinated and contain only an N-terminal fragment of huntingtin. This model should thus be useful in studying a processing step that is likely to be important in the pathogenicity of mutated huntingtin.

Animals↗

PubMed1999

Versatile copurification procedure for rapid isolation of homogeneous RAR-RXR heterodimers.

RAR-RXR heterodimeric complexes (RARalphaDeltaAB-RXRalphaDeltaAB) bound to cognate DR5 DNA response elements were purified to apparent structural and functional homogeneity using a novel versatile immobilized metal affinity chromatography (IMAC) copurification procedure. Dynamic light scattering studies indicated that the complexes were more than 85% monodisperse. By electron microscopy the negatively stained RAR-RXR-DNA complexes appeared homogeneous and corresponded to a dimeric arrangement of the molecules. Using heterodimers purified according to this procedure we demonstrate ligand binding of RXR in the context of the RAR-RXR heterodimer-DNA complex. The present copurification procedure is rapid and has yielded high quality heterodimer-DNA complexes suitable for both structural and biochemical studies.

Chromatography, Affinity↗

PubMed1999

Self-assembly of soluble proteins on functionalized lipid layers: a tentative correlation between the fluidity properties of the lipid film and protein ordering.

New series of amphiphilic structures are designed to exhibit various fluidity properties when spread at the air-water interface. The influence of the molecular structure of these lipids on the process of two-dimensional (2D) crystallization of the B subunit of DNA gyrase, a soluble protein, is investigated in terms of size of the crystals produced, protein ordering, and crystallization kinetics. Whereas no difference is observed concerning the mean size of the protein 2D crystals obtained on the different lipid supports, the ultimate protein ordering observable by electron microscopy using the negative-staining technique is more regularly attained with some of these new lipids. The most interesting point results from large discrepancies in crystallization kinetics as highly-ordered protein 2D crystals form within 6-24 h depending on the lipid layer structure. Thus, these new lipids reveal of special interest when studying proteins that suffer from extended incubation time at 4 degrees C or higher temperature and lose their functionality.

Crystallization↗

PubMed1999

Importance of the fraction of microcrystalline cellulose and spheronization speed on the properties of extruded pellets made from binary mixtures.

The aim of the study was to prove the importance of the binary mixture composition and spheronization speed on pellet properties. Extrudates from different binary mixtures of microcrystalline cellulose (MCC) and dicalcium phosphate dihydrate were prepared with a power-consumption-controlled extruder and spheronized at different speeds. The water content of the extrudate for the production of spherical pellets was evaluated. The pellets were characterized in terms of size, shape, porosity, mechanical properties, and disintegration. The fraction of MCC in the binary mixtures had the highest impact on the pellet properties. With an increasing fraction of MCC more water was required for successful pelletization, size and porosity of the pellets decreased, and the surface tensile stress increased. These observations were evaluated using the "sponge" and the "crystallite--gel" models for MCC. The latter led to the conception that an extrudate consists of two phases: a percolating crystallite--gel phase formed by MCC and water during extrusion and a filler phase formed by the second component of the binary mixture. This two-phase concept provides explanations for the extent of shrinking during drying and for the disintegration behavior. The spheronization speed had an influence on the size but not on porosity or surface tensile stress of the pellets. The best results were obtained at intermediate spheronization velocities of 10 and 13.4 m/sec. Fundamental properties of extrudates and pellets can be described by applying a two-phase concept of the crystallite--gel model.

Algorithms↗

PubMed1998

The RNA cleavage activity of RNA polymerase III is mediated by an essential TFIIS-like subunit and is important for transcription termination.

Budding yeast RNA polymerase III (Pol III) contains a small, essential subunit, named C11, that is conserved in humans and shows a strong homology to TFIIS. A mutant Pol III, heterocomplemented with Schizosaccharomyces pombe C11, was affected in transcription termination in vivo. A purified form of the enzyme (Pol III Delta), deprived of C11 subunit, initiated properly but ignored pause sites and was defective in termination. Remarkably, Pol III Delta lacked the intrinsic RNA cleavage activity of complete Pol III. In vitro reconstitution experiments demonstrated that Pol III RNA cleavage activity is mediated by C11. Mutagenesis in C11 of two conserved residues, which are critical for the TFIIS-dependent cleavage activity of Pol II, is lethal. Immunoelectron microscopy data suggested that C11 is localized on the mobile thumb-like stalk of the polymerase. We propose that C11 allows the enzyme to switch between an RNA elongation and RNA cleavage mode and that the essential role of the Pol III RNA cleavage activity is to remove the kinetic barriers to the termination process. The integration of TFIIS function into a specific Pol III subunit may stem from the opposite requirements of Pol III and Pol II in terms of transcript length and termination efficiency.

Amino Acid Sequence↗

PubMed1998

Specific interaction and two-dimensional crystallization of histidine tagged yeast RNA polymerase I on nickel-chelating lipids.

Nickel-chelating lipid monolayers were used to generate two-dimensional crystals from yeast RNA polymerase I that was histidine-tagged on one of its subunits. The interaction of the enzyme with the spread lipid layers was found to be imidazole dependent, and the formation of two-dimensional crystals required small amounts of imidazole, probably to select the specific interaction of the engineered tag with the nickel. Two distinct preparations of RNA polymerase I tagged on different subunits yielded two different crystal forms, indicating that the position of the tag determines the crystallization process. The orientation of the enzyme in both crystal forms is correlated with the location of the tagged subunits in a three-dimensional model which shows that the tagged subunits are in contact with the lipid layer.

Chelating Agents↗

PubMed1997

A shared subunit belongs to the eukaryotic core RNA polymerase.

The yeast RNA polymerase I is a multimeric complex composed of 14 distinct subunits, 5 of which are shared by the three forms of nuclear RNA polymerase. The reasons for this structural complexity are still largely unknown. Isolation of an inactive form of RNA Pol I lacking the A43, ABC23, and A14 subunits (RNA Pol I delta) allowed us to investigate the function of the shared subunit ABC23 by in vitro reconstitution experiments. Addition of recombinant ABC23 alone to the RNA Pol I delta reactivated the enzyme to up to 50% of the wild-type enzyme activity. The recombinant subunit was stably and stoichiometrically reassociated within the enzymatic complex. ABC23 was found to be required for the formation of the first phosphodiester bond, but it was not involved in DNA binding by RNA Pol I, as shown by gel retardation and surface plasmon resonance experiments, and did not recycle during transcription. Electron microscopic visualization and electrophoretic analysis of the subunit depleted and reactivated forms of the enzyme indicate that binding of ABC23 caused a major conformational change leading to a transcriptionally competent enzyme. Altogether, our results demonstrate that the ABC23 subunit is required for the structural and functional integrity of RNA Pol I and thus should be considered as part of the core enzyme.

DNA↗

PubMed1997

Use of a mass-thickness marker to estimate systematic errors and statistical noise in the detection of phosphorus by electron spectroscopic imaging.

The element signal obtained from electron-energy-filtered micrographs depends on the systematic error in calculating the background and on the noise in the background-corrected image. Both systematic error and statistical fluctuation of the background can be assessed experimentally with a specimen that combines the element-containing feature with a mass-thickness marker. The approach is described for the mapping of phosphorus in turnip yellow mosaic viruses prepared on a supporting carbon film of variable thickness. The thickness modulations are produced by the additional deposition of heat-evaporated carbon through a second grid used as a mask. The three-window power-law method and the two-window difference method are compared. With the three-window power-law method, the mass-thickness modulations of the marker are still visible in the map, indicating a systematic error for the calculated background. In addition, the intensity profile over the area of the thick carbon film is broader than in the map corrected by the two-window method, indicating a higher level of noise. With the two-window difference method, mass-thickness contrast was practically eliminated due to an improved protocol that uses the mass-thickness marker to calculate the scaling factor: instead of scaling the grey-level of a single background feature, the pre-edge image is scaled to the contrast of the marker area in the image acquired at the element-specific energy loss.

Electron Probe Microanalysis↗

PubMed1997

The 22q11.2 deletion: screening, diagnostic workup, and outcome of results; report on 181 patients.

A submicroscopic deletion of chromosome 22q11.2 has been identified in the majority of patients with the DiGeorge syndrome, velocardiofacial syndrome, conotruncal anomaly face syndrome, and in some patients with isolated conotruncal cardiac anomalies, Opitz G/BBB syndrome, and Cayler cardiofacial syndrome. We have evaluated 181 patients with this deletion. We describe our cohort of patients, how they presented, and what has been learned by having the same subspecialists evaluate all of the children. The results help define the extremely variable phenotype associated with this submicroscopic deletion and will assist clinicians in formulating a management plan based on these findings.

Abnormalities, Multiple↗

PubMed1997

HRTEM study of biological crystal growth mechanisms in the vicinity of implanted synthetic hydroxyapatite crystals.

Calcium phosphates are widely used as biomaterials. Ultrastructural assessments are of the utmost importance in our understanding of interfacial phenomena. The aim of this study was to learn more about the newly formed crystal growth mechanisms. The interfaces between implanted synthetic hydroxyapatite crystals (HAS) and newly formed crystallites were thoroughly examined on a molecular level. The bone-grafting material (HAS) was implanted into two adult patients, and small biopsies were recovered 6 months after implantation. The raw biomaterial was analyzed by x-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Six months after their implantation, the HAS aggregates were surrounded by a mineralized bone matrix. Tiny crystallites also filled the spaces between the HAS crystals within the aggregates. These newly formed crystallites growing at the surfaces of the implanted HAS crystals appeared to be apatitic. The crystallographic investigations of the nucleation and growing mechanisms of the newly formed crystallites were performed by HRTEM in association with computer simulation and mathematical processing of digitized images. A relationship was noted between the orientation axes of crystallites growing nearby and the zone axes of the implanted HAS, thus strongly suggesting a guiding or substratum role of the HAS particles.

Adult↗

PubMed1997

High resolution electron microscopy: structure and growth mechanisms of human dentin crystals.

Biological crystal formation was postulated to begin by a nucleation process. Such processes have been demonstrated for human amelogenesis and bone mineralization. The aim of this study was to confirm if such mechanisms occur during dentin crystal formation. The structure of human fetal dentin crystals and the earliest stages of mineral growth were followed by High Resolution Electron Microscopy (HREM) associated with digitalized image analysis. Micrographs of the mineralization front were first digitalized, and selected areas were transformed in the reciprocal space by Fast Fourier Transform. The resulting diffractograms were compared with computer-simulated diffractograms and used to determine the orientation of crystals. Dentin crystals, found close to the mineralization front, show a structure closely related to that of hydroxyapatite (HA), as determined by comparison of HREM images with simulated images. These crystals present numerous structural defects such as dislocations and grain boundaries. These defects appear to be present in dentin crystals at an early stage of growth. We have also observed nanometer-sized particles in mineralization areas. Calculated diffractograms of these areas show significant similarities with HA diffraction patterns, and in one case, their structure could be correlated to HA structure through an image simulation process. These nanometer-sized particles could be related to the nucleation process, and their growth, orientation, and formation appear to be mediated by extracellular matrix components.

Crystallization↗

PubMed1997

Resolution of RNA polymerase I into dimers and monomers and their function in transcription.

We have further analyzed the requirements of yeast RNA polymerase I (pol I) to initiate transcription at the ribosomal gene promoter. Resolution of yeast whole cell extracts through several chromatographic steps yielded three protein fractions required for accurate initiation. One fraction is composed of TBP associated within a 240 kDa protein complex. The fraction contributing the RNA polymerase I (pol I) activity consists of dimeric and monomeric pol I under conditions optimal for in vitro transcription. The capability to utilize the ribosomal gene promoter correlates with monomeric pol I complexes which are possibly associated with further transcription factors. These initiation competent pol I complexes appeared to be resistant to high salt concentrations. Pol I dimers which represent the majority of the isolated pol I, can be reversibly dissociated into monomers and are only active in non-specific RNA synthesis, if single stranded DNA serves as a template. We suggest a model in which dimeric inactive pol I is converted into an active monomeric form that might be associated with other transcription factors to maintain a stable initiation competent complex.

Dimerization↗

PubMed1997

Detection of a 22q11.2 deletion in cardiac patients suggests a risk for velopharyngeal incompetence.

OBJECTIVE: Conotruncal cardiac anomalies frequently occur in patients with DiGeorge or velocardiofacial syndrome. Additionally, these patients may have overt or submucousal cleft palate, as well as velopharyngeal incompetence (VPI). Previous studies have demonstrated that the majority of these patients have a submicroscopic deletion of chromosome 22q11.2. We hypothesized that a subpopulation of newborns and children with congenital heart defects caused by a 22q11.2 deletion are at a high risk for having unrecognized palatal abnormalities. Therefore, we proposed to evaluate a cohort of patients with conotruncal cardiac malformations associated with a 22q11.2 deletion to determine the frequency of palatal abnormalities. METHODS: We identified 14 deletion-positive patients with congenital cardiac defects who had no overt cleft palate. Of the 14 patients evaluated for the 22q11.2 deletion, 8 patients were recruited from a previous study looking for deletions among patients with isolated conotruncal cardiac anomalies. Informed consent was obtained in these cases. The remaining patients had the deletion study on a clinical basis, ie, conotruncal cardiac defect and an absent thymus, immunodeficiency, or minor dysmorphia appreciated by the clinical geneticist. These patients were evaluated by a plastic surgeon and speech pathologist looking for more subtle palatal anomalies such as a submucousal cleft palate, absence of the musculous uvuli, and VPI. Some patients underwent videofluoroscopy or nasendoscopy depending on their degree of symptoms and age. VPI was not ruled out until objective evaluation by a speech pathologist and plastic surgeon was obtained. In addition, the child had to be old enough to provide an adequate speech sample. RESULTS: Of the 14 patients evaluated, 6 patients older than 1 year were found to have VPI. It is noteworthy that 3 of these patients were older than 5 years and had remained unrecognized until this study. The remaining 6 patients had inconclusive studies based on their age (younger than 26 months) and their inability to participate in adequate speech evaluations. Two of these patients, however, had histories of nasal regurgitation suggesting VPI and, in addition, had incomplete closure of the velopharyngeal mechanism during crying and swallowing observed during nasendoscopic examination-consistent with the diagnosis of VPI. Thus, 8 of 14 patients evaluated had evidence of VPI by history and examination. The remaining 6 patients will require further study when they are older before a definitive palatal diagnosis can be made. CONCLUSIONS: A significant number of patients with a 22q11.2 deletion in a cardiac clinic may have unrecognized palatal problems. Recognition of such abnormalities will afford patients the opportunity for intervention as needed, ie, speech therapy and/or surgical intervention. Notably, two of our patients with findings suggesting VPI were infants and will, therefore, be afforded the opportunity for close follow-up and early intervention. Furthermore, three school-aged children had palatal abnormalities that were unrecognized until this study. Thus, we recommend 22q11.2 deletion studies in patients with conotruncal cardiac malformations, followed by extensive palatal and speech evaluations when a deletion is present.

Abnormalities, Multiple↗

PubMed1996

Localization of yeast RNA polymerase I core subunits by immunoelectron microscopy.

Immunoelectron microscopy was used to determine the spatial organization of the yeast RNA polymerase I core subunits on a three-dimensional model of the enzyme. Images of antibody-labeled enzymes were compared with the native enzyme to determine the localization of the antibody binding site on the surface of the model. Monoclonal antibodies were used as probes to identify the two largest subunits homologous to the bacterial beta and beta' subunits. The epitopes for the two monoclonal antibodies were mapped using subunit-specific phage display libraries, thus allowing a direct correlation of the structural data with functional information on conserved sequence elements. An epitope close to conserved region C of the beta-like subunit is located at the base of the finger-like domain, whereas a sequence between conserved regions C and D of the beta'-like subunit is located in the apical region of the enzyme. Polyclonal antibodies outlined the alpha-like subunit AC40 and subunit AC19 which were found co-localized also in the apical region of the enzyme. The spatial location of the subunits is correlated with their biological activity and the inhibitory effect of the antibodies.

Amino Acid Sequence↗

PubMed1996

Structure and conformational changes of DNA topoisomerase II visualized by electron microscopy.

Type II DNA topoisomerases, which create a transient gate in duplex DNA and transfer a second duplex DNA through this gate, are essential for topological transformations of DNA in prokaryotic and eukaryotic cells and are of interest not only from a mechanistic perspective but also because they are targets of agents for anticancer and antimicrobial chemotherapy. Here we describe the structure of the molecule of human topoisomerase II [DNA topoisomerase (ATP-hydrolyzing), EC 5.99.1.3] as seen by scanning transmission electron microscopy. A globular approximately 90-angstrom diameter core is connected by linkers to two approximately 50-angstrom domains, which were shown by comparison with genetically truncated Saccharomyces cerevisiae topoisomerase II to contain the N-terminal region of the approximately 170-kDa subunits and that are seen in different orientations. When the ATP-binding site is occupied by a nonhydrolyzable ATP analog, a quite different structure is seen that results from a major conformational change and consists of two domains approximately 90 angstrom and approximately 60 angstrom in diameter connected by a linker, and in which the N-terminal domains have interacted. About two-thirds of the molecules show an approximately 25 A tunnel in the apical part of the large domain, and the remainder contain an internal cavity approximately 30 A wide in the large domain close to the linker region. We propose that structural rearrangements lead to this displacement of an internal tunnel. The tunnel is likely to represent the channel through which one DNA duplex, after capture in the clamp formed by the N-terminal domains, is transferred across the interface between the enzyme's subunits. These images are consistent with biochemical observations and provide a structural basis for understanding the reaction of topoisomerase II.

Adenosine Triphosphate↗