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At least 775 records · Page 43Linked to original sources
PubMed2000

Subtractive hybridization used to identify mRNA associated with the maturation of bovine oocytes.

The main objective of this project is to identify mRNA associated with oocyte maturation and embryonic developmental competency. The knowledge of genes and their accumulated mRNA is essential to better understand the mechanisms involved in the oocyte maturation and the survival of the in vitro produced embryo. We used bovine slaughterhouse-recovered ovaries and collected the oocytes from two follicle size categories: <2 mm and 3-5 mm. The mRNA content of oocytes from follicles 3-5 mm where considered to be more competent when compared to the content of oocytes from follicles <2 mm. In this report we compare two different technical approaches both involving PCR to compare the mRNA pools of the oocytes. In the first approach we performed the differential display (DDRT) technique to amplify and display side by side the cDNAs of groups of 10 denuded oocytes. From this approach, we isolated 28 different bands. After analysis, three of those bands had strong homology with known genes. In the second approach pools of 50 denuded oocytes were submitted to suppressive subtraction hybridization (SSH). We identified several known genes like cyclin B1, splicing factor ccl.4, cytochrome c oxidase, and mineralocorticoid receptor while numerous other clones remain unidentified. The cyclin B1 clone was used as a probe to evaluate its follicular size specificity on virtual Northern blot. The PCR basis of these techniques allows comparison of mRNA from tissues of low abundance such as oocytes. In this study the SSH resulted in longer clones than DDRT and showed high specificity.

Animals↗
PubMed1983

Permeation of skin and eschar by antiseptics II: influence of controlled burns on the permeation of phenol.

The safe antiseptic use of phenol over the burn-traumatized surface depends on knowledge of how the systemic accumulation of phenol is affected by burn processes. To gain insight into the underlying permeation phenomenon, the diffusion of phenol and a reference cosolute, methanol, through both scalded and branded dorsal skin sections of the hairless mouse was studied as a function of burn temperature using in vitro diffusion cells. Temperatures up to 100 and 150 degrees were used for scalding and branding, respectively, using a 60-sec; exposure time. Permeability coefficients of the traumatized skins were assessed at 37 degrees and compared with control values. Coefficients of both permeating species were not increased significantly by burn temperatures up to 70 degrees applied either by scalding or branding, however, at higher temperatures exaggerated increases in permeation rates were noted. A limiting increase of approximately 7 times the control value was noted for phenol irrespective of the burn method. Permeability of methanol was altered even more dramatically and at 100 degrees by scalding and 150 degrees by branding was over 50 times the control rate. At 80 and 100 degrees for methanol and at 80 degrees for phenol, scalding produced larger increases in the permeability coefficients than branding. Since contact for 1 min at 60 degrees is capable of producing a full-thickness burn injury, it is clear that eschar permeability to phenol immediately postburn is not related to the clinical degree of burning, but is a function of the thermal intensity (hotness) of the burn stimulus. Full-thickness wounds can be expected to have highly variable rates of systemic absorption as a direct consequence of the wide-ranging permeability possible for such burns, with the risks of topical application varying accordingly.

Animals↗
PubMed1978

[The colony forming cell and its stimulation--findings in hematological diseases (author's transl)].

In modifying the agar culture technique of mouse bone marrow cells Robinson et al. in 1970 described the in vitro culture of the human colony-forming cell. Since that time a number of data accumulated which markedly improved our knowledge of the regulation of normal and pathological hematopoiesis. A summary of the up-to date results is presented focusing mainly on disturbances of the colony-forming cells in peripheral blood and bone marrow of patients with hematological disorders. Furthermore, the findings on human urinary CSF excretion which exerts an action on mouse bone marrow are discribed. The somewhat contradictory results obtained with different methods are discussed in the light of the actual hypotheses.

Adult↗
PubMed1995

[Scientific change in times of political upheaval: Germany in the 20th century].

Until recently, the development of the modern sciences has usually been described as a continuous unfolding of constantly expanding and differentiating research institutions on the one hand, and the accumulation of more and better knowledge on the other. The changes that have occurred both in scientific institutions and in the direction and content of research in the course of revolutions or comparable political changes pose significant challenges to such accounts. I would like to propose an interactive approach to this issue. Instead of accepting a linear, deterministic model of scientific change as a result of political upheaval, I suggest that such political changes present an array of challenges to and possibilities for the interruption, redirection, reconstruction or effortful continuation of research. The central claim is that scientific development in times of political upheaval has proceeded in Germany primarily by means of increasing cooperation of scientists with the state, involving a process that I call the technologization of basic research. But this is not always a one-sided affair involving the subordination of science to practical politics or to ideology. Rather, I argue, what occurs is the mobilization or reconstruction of physical, institutional, financial cognitive and/or rhetorical resources. Such mobilizations can proceed in various directions: the state or agencies within it can mobilize scientists as resources in the interest of achieving certain political aims; scientists can convert themselves into such resources (or claim that they are doing so); or both things can happen at once. The approach is exemplified by examining continuities and changes in the situations of the sciences following the major turning points of 20th century German history, symbolized by the dates 1918, 1933, 1945 and 1990. Considered in particular are: scientific changes in Germany following the Nazi takeover and creative innovations by émigré scientists working in different cultural settings; the massive transfer of scientific resources after Nazi Germany's defeat and attempts to carry on and reconstruct science in the two postwar German states; and the massive reorganization of scientific institutions in eastern Germany after unification. The examples come primarily from biology and experimental psychology, but physical sciences and particular branches of technology are considered as well.

Germany↗
PubMed2005

Iatrogenic carotid artery injury in neurosurgery.

Iatrogenic carotid artery injury (CAI) results from various neurosurgical procedures. A review of the literature was conducted to provide an update on the management of this potentially devastating complication. Iatrogenic CAIs are categorized according to each diagnostic or therapeutic procedure responsible for the injury, i.e., anterior cervical spine surgery, central venous catheterization, chemical substances, chiropractic manipulation, diagnostic cerebral angiography, middle-ear surgery, percutaneous procedures for trigeminal neuralgia, radiation therapy, skull-base surgery, tracheostomy, and transsphenoidal surgery. The incidence, mechanisms of injury, diagnostic imaging modalities, and reparative procedures are discussed for each procedure. Iatrogenic CAI may be more prevalent than had previously been thought, mostly because of a heightened awareness on the part of physicians and the earlier detection of asymptomatic patients owing to sophisticated and less-invasive imaging modalities. Prevention is the best treatment for every iatrogenic injury, and it is expected that further accumulation of experience with and knowledge of iatrogenic CAI will result in further reduction of this complication. Although some CAIs, such as radiation-induced carotid artery stenosis, may not be preventable, earlier intervention before the patient becomes symptomatic may favorably alter the prognosis. Following the rapid development of endovascular techniques in recent years, surgically inaccessible lesions can be treated in a more reliable and safe manner than before.

Carotid Artery Injuries↗
PubMed1989

Power and pain: the location of pain and fear in dentistry and the creation of a dental subject.

It has been argued that the meaning of pain in childbirth and in general medicine has changed and that this change was part of a cognitive transformation that occurred in medicine during the post World War II period. This paper uses Foucault's notion of the gaze and his unique conception of power to explore the extent to which the understanding of pain, and the associated concept of fear, in dentistry, reflects those understandings found in medicine and obstetrics. Within the discourse of dentistry the conception of pain is both object and effect of the profession's techniques of observation and analysis. Analyses of pain and fear occurred on two levels: the micro-level of the individual and the macro-level of the population. The examples of the case history and the epidemiological survey are used to demonstrate these two levels of power/knowledge. The first technique contributed to the constitution of the psychological space, the second technique confirmed the social space. Within these spatialisations new conceptualisations of pain were realised and a subjective dental subject was manufactured. The findings of this paper add weight to the thesis that the functioning of power/knowledge transcends professional and disciplinary boundaries and is a process which is far more subtle and fundamental than one of political manoeuverings by interested groups or individuals or the accumulation of an increasingly sophisticated knowledge.

Dentist-Patient Relations↗
PubMed2005

Practical considerations in PTH testing.

New knowledge concerning PTH biology have accumulated during the past few years. The finding that the so-called "intact" PTH assays measure a "non-1-84" PTH fragment in addition to full-length PTH has led to the development of new assays. These new assays, which were initially thought to measure 1-84 PTH only, have been shown to recognize also another PTH species called "amino-PTH". As the various names given to the different assay methods are highly confusing, there is a need for a simplified nomenclature. A simple way would be to identify the older "intact" PTH assays as second-generation assays and the new assays (Whole, CAP, BioIntact) as third-generation assays. Although of considerable potential interest for the comprehension of PTH physiology, the third-generation PTH assays have not yet proved to be superior to the second-generation assays in clinical practice. There is thus currently no recommendation to switch from the second-generation to the third-generation assays in clinical practice, or to use a ratio derived from the concommitent measurement of PTH with both assay-generation. Because second- and third-generation PTH assays are usually highly correlated, significant differences in the clinical information provided by these methods are unlikely. However, our opinion is that more definitive bone biopsy studies in dialyzed patients selected according to their bone- and calcium-related treatment are still needed to reach a consensus. Finally, we have proposed that PTH reference values should be established in healthy subjects with a normal vitamin D status. This supposes that 25OHD is measured in the reference population beforehand, and that the subjects with vitamin D insufficiency are eliminated from the reference group. Although more complicated than the usual way to establish normative data, we have shown that it decreases the upper limit of normal by 25-35%, enhancing thus the diagnostic sensitivity for hyperparathyroidism without a decrease in specificity.

Chronic Kidney Disease-Mineral and Bone Disorder↗
PubMed2004

Dentists' molar restoration choices and longevity: a web-based survey.

STATEMENT OF PROBLEM: The increasing trend toward esthetics has led to controversy as to the longevity of esthetic restorations and the wisdom of having traditional restorations replaced for esthetic reasons. With the assumption that the way dentists treat their own teeth may be a good indication of the accumulated wisdom of the profession, knowledge of dentists' own restorative choices may provide guidance in selecting the most appropriate restorations. PURPOSE: The purpose of this article was to determine restorative choices of dentists for personal molars and estimate restoration longevity. MATERIAL AND METHODS: Information about dentists' molars was obtained from a Web-based survey designed to receive dentists' demographic data and charting of 8 molar teeth with estimated longevity. Approximately 12,000 e-mails asking to access the website were sent to dentists' addresses randomly selected from a commercial database. Nonrespondents received 1 reminder. The responses were statistically analyzed with a chi-square analysis (alpha=.05). RESULTS: Seven hundred fifty-seven valid replies provided information for 6,034 teeth (22% unrestored, 75% restored, 2% missing). Restorations reported included amalgam (36%), gold inlay/onlay (13%), complete veneer crown (CVC) (10%), metal-ceramic crown (MCC) (8%), and composite (7%). Other esthetic options accounted for less than 3%. Restorations with more than 20 years longevity included amalgam restorations (58%), gold inlays/onlays (48%) and crowns (23%). Fifty-six percent of esthetic restorations and 5% of amalgams were placed in the last 5 years. The following restorations were placed in the last year (n=186): 38% esthetic, 29% crowns (18% MCC; 11% CVC), and 17% gold inlay/onlay or amalgam. Significant differences (P<.001) were identified for dentist's gender, year of graduation and practice location. CONCLUSIONS: Most dentists have not replaced traditional metallic restorations with esthetic alternatives. Dentists still choose nonesthetic options for significant numbers of their own restorations.

Attitude of Health Personnel↗
PubMed2005

Structural studies of the human PBAF chromatin-remodeling complex.

ATP-dependent chromatin remodeling is one of the central processes responsible for imparting fluidity to chromatin and thus regulating DNA transactions. Although knowledge on this process is accumulating rapidly, the basic mechanism (or mechanisms) by which the remodeling complexes alter the structure of a nucleosome is not yet understood. Structural information on these macromolecular machines should aid in interpreting the biochemical and genetic data; to this end, we have determined the structure of the human PBAF ATP-dependent chromatin-remodeling complex preserved in negative stain by electron microscopy and have mapped the nucleosome binding site using two-dimensional (2D) image analysis. PBAF has an overall C-shaped architecture--with a larger density to which two smaller knobs are attached--surrounding a central cavity; one of these knobs appears to be flexible and occupies different positions in each of the structures determined. The 2D analysis of PBAF:nucleosome complexes indicates that the nucleosome binds in the central cavity.

Binding Sites↗
PubMed2001

Mitogen-activated protein [MAP] kinase pathways in plants: versatile signaling tools.

Mitogen-activated protein kinases (MAPKs) are important signaling tools in all eukaryotes, and function in mediating an enormous variety of external signals to appropriate cellular responses. MAPK pathways have been studied extensively in yeast and mammalian cells, and a large body of knowledge on their functioning has accumulated, which is summarized briefly. Plant MAPK pathways have attracted increasing interest, resulting in the isolation of a large number of different components of MAPK cascades. Studies on the functions of these components have revealed that MAPKs play important roles in the response to a broad variety of stresses, as well as in the signaling of most plant hormones and in developmental processes. Finally, the involvement of various plant phosphatases in the inactivation of MAPKs is discussed.

Cell Cycle↗
PubMed2000

Kaposi's sarcoma. New treatment modalities.

Over the last 20 years of experience with the AIDS epidemic, we have accumulated a great body of knowledge on Kaposi's sarcoma (KS), a major cause of morbidity and mortality in AIDS patients, especially among homosexual and bisexual men. New antiretroviral therapies, in particular the protease inhibitors, appear to be changing the clinical course of KS. Now, it is not unusual to observe a complete resolution and control of KS with the use of these new agents. As we have begun to unravel the pathogenesis of KS, new treatment modalities have merged targeting some of its pathogenic pathways. Although, chemotherapy remains the cornerstone of its treatment, in particular with the new liposomal preparations, new agents may soon change our approach to KS. Experimental therapies being evaluated in ongoing clinical trials include angiogenesis inhibitors, hormonal therapies, retinoic acid derivatives, and immune modulators such as interleukin 12. Better treatment for HIV, and new experimental therapies targeting the pathogenic mechanisms of KS allow us to envision the future treatment of KS with a certain degree of optimism.

Biological Products↗
PubMedDate not supplied

Women's ways of knowing in nursing and critical thinking.

The purpose of this longitudinal qualitative study was (1) to extend the work of Belenky, Clinchy, Goldberger, and Tarule by interviewing female university nursing students to determine their "way of knowing" according to the Women's Ways of Knowing (WWK) schema and (2) to determine what relationship this way of knowing might have with critical thinking when accumulating a specific body of knowledge such as nursing. Interviews were conducted with 21 sophomore nursing students. Fourteen were reinterviewed their junior year, and 10 were interviewed or participated in a focus group their senior year. The procedural knowledge categories of separate and connected knowing became the focus of data analysis through the constant comparative method. Procedures for connected knowing were illuminated. Connected knowing was found to be congruent with nursing and the ways these women wanted to be as nurses. Separate knowing was found to be incongruent with nursing except for critical thinking purposes. Contrary to the notion that critical thinking is principled rather than procedural, procedural knowing, according to WWK, became the principle on which these women based their nursing actions, moving them to constructed knowers and caring, critical thinkers as they experienced nursing education.

Adult↗
PubMed2001

Global context effect in normal and scrambled musical sequences.

The processing of chords is facilitated when they are harmonically related to the context in which they appear. The purpose of this study was to assess whether this harmonic priming effect depends on the version (normal vs. scrambled) of the context chord sequences. Normal sequences were scrambled by permuting chords two-by-two (Experiment 1) or four-by-four (Experiments 2 and 3). Normal chord sequences were judged less coherent than scrambled sequences. However, normal chord sequences showed facilitation for harmonically related rather than for unrelated targets, and this effect of relatedness did not diminish for scrambled sequences (Experiments 1-3). The data of musicians and nonmusicians were interpreted with Bharucha's (1987) spreading activation framework. Simulations suggested that harmonic priming results from activation that spreads via schematic knowledge of Western harmony and accumulates in short-term memory over the course of the chord sequence.

Auditory Perception↗
PubMed2002

DNA methylation and breast carcinogenesis.

Knowledge about breast carcinogenesis has accumulated during the last decades but has barely been translated into strategies for early detection or prevention of this common disease. Changes in DNA methylation have been recognized as one of the most common molecular alterations in human neoplasia and hypermethylation of gene-promoter regions is being revealed as one of the most frequent mechanisms of loss of gene function. The heritability of methylation states and the secondary nature of the decision to attract or exclude methylation support the idea that DNA methylation is adapted for a specific cellular memory. According to Hanahan and Weinberg, there are six novel capabilities a cell has to acquire to become a cancer cell: limitless replicative potential, self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, evasion of programmed cell death, sustained angiogenesis and tissue invasion and metastasis. This review highlights how DNA-methylation contributes to these features and offers suggestions about how these changes could be prevented, reverted or used as a 'tag' for early detection of breast cancer or, preferably, for detection of premalignant changes.

Breast Neoplasms↗
PubMed1998

Multiple mechanisms of action of the benzamides and nicotinamides as sensitizers of radiotherapy: opportunities for drug design.

The benzamides and nicotinamides are a well-known class of drugs that contain many analogs having radio- and chemosensitizing properties. This study reports on a structural analysis in order to explain the chemical features important to their mechanisms of action. In general, N-substituted analogs are distinguished from the non-N-substituted analogs because they (i) are susceptible to radiolysis, (ii) induce cytotoxicity by apoptosis but not necrosis, (iii) inhibit cell proliferation, (iv) activate poly adenosine diphosphate ribosyl transferase (poly ADPRT), and (v) have a much-reduced effect on microregional tumor blood perfusion. It was concluded that the mechanism of action of N-substituted analogs is shifted from primary effects on tumor vascularization as is seen with the non-N-substituted analogs to one where radiosensitization can be explained by selective induction of apoptosis via radiolysis and accumulation of DNA damage. This knowledge may be useful in the design of drugs possessing multiple mechanisms of radiosensitizing action.

Animals↗
PubMed2003

Discrete quantum breathers: what do we know about them?

The knowledge about discrete quantum breathers, accumulated during the last two decades, is reviewed. "Prehistory" of the problem is described and some important properties differentiating localized and extended vibrational modes are outlined. The state of art of our understanding of the principal features of the quantum discrete breathers is presented.

Journal Article↗
PubMed1989

Mitochondrial DNA sequences in single hairs from a southern African population.

Hypervariable parts of mitochondrial DNA (mtDNA) were amplified enzymatically and sequenced directly by using genomic DNA from single plucked human hairs. This method has been applied to study mtDNA sequence variation among 15 members of the !Kung population. A genealogical tree relating these aboriginal, Khoisan-speaking southern Africans to 68 other humans and to one chimpanzee has the deepest branches occurring amongst the !Kung, a result consistent with an African origin of human mtDNA. Fifteen cases of unrelated individuals having identical sequences in the most variable parts of the mtDNA control region were found within populations of !Kung, Western Pygmies, and Eastern Pygmies, but no cases of identity were evident among these populations. This and other evidence of geographic structuring of the mitochondrial diversity in Africa, together with knowledge of the rate of accumulation of base changes in human mtDNA, implies that the average rate at which female lineages have moved their home bases during hunter-gatherer times could be as low as 13 meters per year. The technique of enzymatic amplification and direct sequencing applied to readily collected, highly stable biological materials such as hairs makes it possible to examine with high resolution many representatives of virtually any population.

Africa, Southern↗
PubMed2001

Assessment of ergonomics in laparoscopic surgery.

At Delft University designers are educated to design 'products for people'. Therefore the field of ergonomics has been divided along the human functions: physical, sensorial and cognitive ergonomics. This article gives an overview of the assessment of these aspects of ergonomics in laparoscopic surgery. It is concluded that a systematic approach is needed, in which knowledge that has already been accumulated for different workplaces (for example, in industry) is applied to the surgeon's circumstances. Such an approach would lead to a set of objectively testable ergonomic requirements for all kinds of products that are used by surgeons in the operating room.

Journal Article↗