Meaningful combinations of chemotherapeutic agents     

F Lutz  R Weiss 《Tier?rztliche Praxis》1990,18(3):209-218

It is frequently assumed that, in general, combinations of antibiotics and similar chemotherapeutic agents are more efficient than the single chemotherapeutic, and that they can be combined without disadvantages for the activity of the single component. However, the specific properties of the combined substances, such as their antimicrobial spectrum and resistance, their pharmacokinetics and side effects, as well as their physical properties and formulation, have an enormous impact on the activity of combined chemotherapeutics. They may lead to an advantageous, but also to an indifferent or diminished activity of the combination in patients. Some of the important requirements for an advantageous combination of antibiotics and similarly functioning compounds will be reviewed and ways of avoiding mistakes are described.  相似文献   

Drug-associated aplastic anemia in dogs: eight cases (1984-1988)   总被引：1，自引：0，他引：1  

D J Weiss  J S Klausner 《Journal of the American Veterinary Medical Association》1990,196(3):472-475

Records of 8 dogs with drug-associated aplastic anemia were reviewed. Drugs suspected as being causative included estradiol cyclopentylpropionate (3 dogs), phenylbutazone (2 dogs), meclofenamic acid (1 dog), trimethoprim-sulfadiazine and fenbendazole (1 dog), and quinidine (1 dog). Five of the dogs died or were euthanatized. One dog with estrogen-associated aplasia recovered after prolonged treatment. The dogs with trimethoprim-sulfadiazine and quinidine-associated marrow aplasia recovered promptly after treatment was discontinued.  相似文献   

Norway Spruce: A Novel Method using Surface Characteristics and Heavy Metal Concentrations of Needles for a Large-Scale Monitoring Survey in Austria     

Trimbacher  C.  Weiss  P. 《Water, air, and soil pollution》2004,152(1-4):363-386

Epistomatal wax structure, occurrence of dust, gypsum-crystallites and microorganisms on the needle surfaces and trace metal contents of current-year Norway spruce needles from various Austrian sites with different pollution levels and sources were analyzed. The epistomatal wax structure was assessed with a recently developed quantification method. Generally, sites in the vicinity of various emissions sources (e.g steel works, chemical industry, magnesite/cement works, highways, conurbations) showed significantly stronger degraded wax structures than sites remote from sources. However, between the individual categories of emitters hardly any difference in the degree of the observed wax degradation could be stated. Various pollutants or emission types seem to cause epistomatal wax degradations. For these findings the following methodological prerequisites which were derived from results of the present monitoring survey were taken into account: the epistomatal wax structures of identical trees were found being significantly different between sampling years. The reasons in behind need further clarification. Therefore only data from the same sampling year should be used for site comparisons in relation to pollution status. The occurrence of mechanical abrasions of surface waxes (which may be caused by the steadily rubbing of needles through heavy wind events) was identified as a further excluding factor for site comparisons. Dust particles and gypsum-crystallites were only detected on needles from sites located in the vicinity of emission sources, whereas the occurrence of microorganisms on the needle surfaces was not related to the vicinity of pollution sources. Several heavy metals were found in elevated concentrations in needles close to respective sources (steel works: Fe, Mn, Zn, Pb, Hg; metallurgical works: Fe, Mn, Ni, Mo, Cr, V; highways: Zn, Cu, Pb). Some of these metals (Fe, Mn, Zn, Cu, Cr, V) were also detected in the dust adhering to the needle surface. These results and the relation of higher contents to the denser covering of the needles with dust suggest that recently deposited adhering dust particles are responsible for the higher elemental contents measured in the needles. In contrast to these needle surface parameters, the epistomatal wax quality did not show any relation to the concentration of the investigated heavy metals.  相似文献   

Evidence for substantial variations of atmospheric hydroxyl radicals in the past two decades     

Prinn RG  Huang J  Weiss RF  Cunnold DM  Fraser PJ  Simmonds PG  McCulloch A  Harth C  Salameh P  O'Doherty S  Wang RH  Porter L  Miller BR 《Science (New York, N.Y.)》2001,292(5523):1882-1888

The hydroxyl radical (OH) is the dominant oxidizing chemical in the atmosphere. It destroys most air pollutants and many gases involved in ozone depletion and the greenhouse effect. Global measurements of 1,1,1-trichloroethane (CH3CCl3, methyl chloroform) provide an accurate method for determining the global and hemispheric behavior of OH. Measurements show that CH3CCl3 levels rose steadily from 1978 to reach a maximum in 1992 and then decreased rapidly to levels in 2000 that were lower than the levels when measurements began in 1978. Analysis of these observations shows that global OH levels were growing between 1978 and 1988, but the growth rate was decreasing at a rate of 0.23 +/- 0.18% year(-2), so that OH levels began declining after 1988. Overall, the global average OH trend between 1978 and 2000 was -0.64 +/- 0.60% year(-1). These variations imply important and unexpected gaps in current understanding of the capability of the atmosphere to cleanse itself.  相似文献   

Breast implant fears put focus on biomaterials     

R Weiss 《Science (New York, N.Y.)》1991,252(5010):1059-1060

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Parallel patterns of evolution in the genomes and transcriptomes of humans and chimpanzees     

Khaitovich P  Hellmann I  Enard W  Nowick K  Leinweber M  Franz H  Weiss G  Lachmann M  Pääbo S 《Science (New York, N.Y.)》2005,309(5742):1850-1854

The determination of the chimpanzee genome sequence provides a means to study both structural and functional aspects of the evolution of the human genome. Here we compare humans and chimpanzees with respect to differences in expression levels and protein-coding sequences for genes active in brain, heart, liver, kidney, and testis. We find that the patterns of differences in gene expression and gene sequences are markedly similar. In particular, there is a gradation of selective constraints among the tissues so that the brain shows the least differences between the species whereas liver shows the most. Furthermore, expression levels as well as amino acid sequences of genes active in more tissues have diverged less between the species than have genes active in fewer tissues. In general, these patterns are consistent with a model of neutral evolution with negative selection. However, for X-chromosomal genes expressed in testis, patterns suggestive of positive selection on sequence changes as well as expression changes are seen. Furthermore, although genes expressed in the brain have changed less than have genes expressed in other tissues, in agreement with previous work we find that genes active in brain have accumulated more changes on the human than on the chimpanzee lineage.  相似文献   

Creating favorable geometries for directing organic photoreactions in alkanethiolate monolayers     

Kim M  Hohman JN  Cao Y  Houk KN  Ma H  Jen AK  Weiss PS 《Science (New York, N.Y.)》2011,331(6022):1312-1315

The products of photoreactions of conjugated organic molecules may be allowed by selection rules but not observed in solution reactions because of unfavorable reaction geometries. We have used defect sites in self-assembled alkanethiolate monolayers on gold surfaces to direct geometrically unfavorable photochemical reactions between individual organic molecules. High conductivity and stochastic switching of anthracene-terminated phenylethynylthiolates within alkanethiolate monolayers, as well as in situ photochemical transformations, have been observed and distinguished with the scanning tunneling microscope (STM). Ultraviolet light absorbed during imaging increases the apparent heights of excited molecules in STM images, a direct manifestation of probing electronically excited states.  相似文献   

F-actin and microtubule suspensions as indeterminate fluids   总被引：12，自引：0，他引：12  

R E Buxbaum  T Dennerll  S Weiss  S R Heidemann 《Science (New York, N.Y.)》1987,235(4795):1511-1514

The viscosity of F-actin and microtubule suspensions has been measured as a function of shear rate with a Weissenberg rheogoniometer. At shear rates of less than 1.0 per second the viscosity of suspensions of these two structural proteins is inversely proportional to shear rate. These results are consistent with previous in vivo measurements of the viscosity of cytoplasm. This power law implies that shear stress is independent of shear rate; that is, shear stress is a constant at all shear rates less than 1.0 per second. Thus the flow profile of these fluids is indeterminate, or nearly so. This flow property may explain several aspects of intracellular motility in living cells. Possible explanations for this flow property are based on a recent model for semidilute suspensions of rigid rods or a classical friction model for liquid crystals.  相似文献   

Coronavirus infection induces H-2 antigen expression on oligodendrocytes and astrocytes   总被引：8，自引：0，他引：8  

A Suzumura  E Lavi  S R Weiss  D H Silberberg 《Science (New York, N.Y.)》1986,232(4753):991-993

Infection of the central nervous system by mouse hepatitis virus strain A59, a murine neurotropic coronavirus, induces class I major histocompatibility complex antigens on mouse oligodendrocytes and astrocytes, cells that do not normally express these antigens on their surfaces. This induction, which occurs through soluble factors elaborated by infected glial cells, potentially allows immunocytes to interact with the glial cells and may play a critical role in the pathogenesis of virus-induced, immune-mediated demyelination in the central nervous system.  相似文献   

A persistent untranslated sequence within bacteriophage T4 DNA topoisomerase gene 60   总被引：30，自引：0，他引：30  

W M Huang  S Z Ao  S Casjens  R Orlandi  R Zeikus  R Weiss  D Winge  M Fang 《Science (New York, N.Y.)》1988,239(4843):1005-1012

A 50-nucleotide untranslated region is shown to be present within the coding sequence of Escherichia coli bacteriophage T4 gene 60, which encodes one of the subunits for its type II DNA topoisomerase. This interruption is part of the transcribed messenger RNA and appears not to be removed before translation. Thus, the usual colinearity between messenger RNA and the encoded protein sequence apparently does not exist in this case. The interruption is bracketed by a direct repeat of five base pairs. A mechanism is proposed in which folding of the untranslated region brings together codons separated by the interruption so that the elongating ribosome may skip the 50 nucleotides during translation. The alternative possibility, that the protein is efficiently translated from a very minor and undetectable form of processed messenger RNA, seems unlikely, but has not been completely ruled out.  相似文献