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Biomedical subjects

R Haag

Publications and source records attributed to R Haag.

At least 19 recordsLinked to original sources
PubMed2001

Electron transport through thin organic films in metal--insulator--metal junctions based on self-assembled monolayers.

This paper describes an experimentally simple system for measuring rates of electron transport across organic thin films having a range of molecular structures. The system uses a metal--insulator--metal junction based on self-assembled monolayers (SAMs); it is particularly easy to assemble. The junction consists of a SAM supported on a silver film (Ag-SAM(1)) in contact with a second SAM supported on the surface of a drop of mercury (Hg-SAM(2))--that is, a Ag-SAM(1)SAM(2)-Hg junction. SAM(1) and SAM(2) can be derived from the same or different thiols. The current that flowed across junctions with SAMs of aliphatic thiols or aromatic thiols on Ag and a SAM of hexadecane thiol on Hg depended both on the molecular structure and on the thickness of the SAM on Ag: the current density at a bias of 0.5 V ranged from 2 x 10(-10) A/cm(2) for HS(CH(2))(15)CH(3) on Ag to 1 x 10(-6) A/cm(2) for HS(CH(2))(7)CH(3) on Ag, and from 3 x 10(-6) A/cm(2) for HS(Ph)(3)H (Ph = 1,4-C(6)H(4)) on Ag to 7 x 10(-4) A/cm(2) for HSPhH on Ag. The current density increased roughly linearly with the area of contact between SAM(1) and SAM(2), and it was not different between Ag films that were 100 or 200 nm thick. The current--voltage curves were symmetrical around V = 0. The current density decreased with increasing distance between the electrodes according to the relation I = I(0)e(-beta d(Ag,Hg)), where d(Ag,Hg) is the distance between the electrodes, and beta is the structure-dependent attenuation factor for the molecules making up SAM(1). At an applied potential of 0.5 V, beta was 0.87 +/- 0.1 A(-1) for alkanethiols, 0.61 +/- 0.1 A(-1) for oligophenylene thiols, and 0.67 +/- 0.1 A(-1) for benzylic derivatives of oligophenylene thiols. The values of beta did not depend significantly on applied potential over the range of 0.1 to 1 V. These junctions provide a test bed with which to screen the intrinsic electrical properties of SAMs made up of molecules with different structures; information obtained using these junctions will be useful in correlating molecular structure and rates of electron transport.

Electrons↗
PubMed2001

Dendrimers and hyperbranched polymers as high-loading supports for organic synthesis.

Polymeric supports have become a big necessity for automated synthesis and combinatorial chemistry, yet, the loading capacities of most polystyrene resins are very limited (typically < 1.5 mmol x g(-1)). Dendrimers and hyperbranched polymers have been discussed for this application and now became readily available. These soluble polymers can either be used directly as high-loading supports for substrates, reagents, and catalysts or alternatively in hybrid polymers linked to conventional polystyrene resins.

Journal Article↗
PubMed2001

Inducing effects of dioxin-like polychlorinated biphenyls on CYP1A in the human hepatoblastoma cell line HepG2, the rat hepatoma cell line H4IIE, and rat primary hepatocytes: comparison of relative potencies.

Polychlorinated biphenyls (PCBs) are a group of widespread environmental pollutants. Some non-ortho-substituted congeners with a high likelihood of coplanarity of both aromatic rings have been shown to act like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as agonists of the aryl hydrocarbon receptor (AhR) subsequently leading to adverse effects, such as immunosuppression and tumor promotion. Although there is a broad base of experimental data concerning the toxicity of PCBs in laboratory animals and animal-derived primary cells and cell lines, only few experimental data are available for cells of human origin. As a parameter of AhR activation, induction of CYP1A-mediated 7-ethoxyresorufin O-deethylase (EROD) activity was determined in the human hepatoblastoma cell line HepG2 treated with the PCBs IUPAC Nos. 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, and 189, and with TCDD as a positive control. Compared with results in rat primary hepatocytes and the rat hepatoma cell line H4IIE, treated HepG2 cells showed lower specific EROD activities maximally inducible by TCDD and PCBs, and EC50 values were shifted to higher concentrations. Furthermore, relative potency factors (REPs) for some congeners such as PCBs 81, 126, and 169 greatly differed from those observed in cells derived from rats. Northern blot analyses showed that EROD activities run parallel to changes in CYP1A-specific mRNA contents. The considerable differences in EROD-derived REPs between cells of human and rat origin indicate the need for further investigations in experimental models from different species including humans in order to extend the database of biochemical and toxic responses to PCBs.

Animals↗
PubMed1999

Application of new electrosurgical devices and probes in endoscopic neurosurgery.

Complex demands and new indications in neurosurgery have led to the need for new electrosurgical generators (ESUs). For the first time, newly developed, automatically controlled ESUs make it possible to use extremely small and flexible instruments safely and to achieve reproducible microcuts and microcoagulations. These specifications make them suitable for neuroendoscopic interventions. In a series of more than one hundred patients with different intracranial and intraspinal pathologies the new electrosurgical devices and probes were used not only for coagulation but also for cutting. The main indications were endoscopic ventriculo-cisternostomy, ventriculo-cystostomy, and membranectomy. The electrosurgical generators as well as the bipolar microcoagulation and -cutting probes proved to be safe and effective for neuroendoscopic interventions.

Electrocoagulation↗
PubMed1994

The partial purification and characterization of purine nucleoside phosphorylase from mammalian mitochondria.

Cytosolic purine nucleoside phosphorylase (PNPase) is a well known, and described enzyme which exists in a variety of organisms, both procaryotic and eucaryotic. More recently this enzyme was found in bovine liver mitochondria. The mitochondrial purine nucleoside phosphorylase was purified 63 fold and has a molecular weight of 48-60 kD. From Lineweaver-Burk plots apparent KM's of 23 microM for inosine, 42 microM for deoxyinosine, 40 microM for phosphate, 2 microM for hypoxanthine, and 163 microM for ribose-1-phosphate were calculated. Both 8-aminoguanosine (Ki = 0.5 microM) and araG (Ki = 381 microM) are inhibitors of the enzyme. The protein's isoelectric point (pI) was calculated at a pH of 4.2. Preliminary immunological work showed no cross-reactivity between epitopes on the mitochondrial protein and those on PNPase from human erythrocytes. The apparent KM's calculated for the mitochondrial enzyme are, with the exception of that using hypoxanthine, within the range commonly associated with KM's from the cytosolic species. The mitochondrial enzyme's molecular weight and pI are less than normally described. The enzyme's isolation from mitochondria, together with several unique characteristics, suggest that it is a separate protein from that found in the cytosol.

Animals↗
PubMed1994

Medico-legal investigations of the Airbus, A320 crash upon Mount Ste-Odile, France.

The authors present the medico-legal investigations and identification after the aircrash of the Airbus A320 upon the Mount Sainte-Odile (France). The identification team comprising investigators from the gendarmerie, forensic pathologists, odontologists, and scientists of the Institute from Legal Medecine rapidly retrieved and identified 85 of the 87 victims, with 17 being identified through DNA typing, three through fingerprints and the remaining through dental records and specific physical or X-ray findings. Full autopsies were performed on all fatalities to determine patterns of injury and cause of death. Results lead us to point out the importance of a multidisciplinary team of forensic practitioners especially trained for managing medico-legal investigation in mass disaster and the ability of DNA technology to solve complex identification problems.

Accidents, Aviation↗
PubMed1991

[Subjectively experienced anxiety as an aspect of coping with illness in children with malignant diseases].

The present paper focuses the perceived anxiety of pediatric oncologic patients (N = 30) at the time of medical treatment. Comparison with a control group of not chronically ill patients (N = 20) results: Children and adolescents with oncologic diseases are reporting significant less anxiety; this is relatively independent of the asked objects and situations. The invasiveness of treatment (applied chemotherapy or not) does not show any influence on the amount of perceived anxiety of oncological patients. Based on current empirical and conceptual findings of coping with serious illnesses the self reported diminished anxiety of pediatric oncologic patients is termed intraphysical "denial" coping mode. The issue of adaptivity is discussed. Finally, initial consequences for psychosocial care of pediatric oncologic patients are described.

Adaptation, Psychological↗
PubMed1989

[Diagnostic approach to basocellular nevomatosis from a dental point of view. Apropos of a new case].

A new case of basal cell naevomatosis, localized in the jaws as odontogenic keratocysts, is described and the importance of the diagnostic role plaid by the dentist is underlined. Skin lesions, bone involvements and the hereditary character of the disease are described. Special emphasis is given to the importance and the easy accessibility of the oral manifestations. Possible evolution towards advanced forms, and the heterogeneity of the symptoms lay the stress on the need of an early diagnosis and the necessity of a close collaboration with the various specialists concerned.

Adult↗
PubMed1989

[The role of mechanical factors in the development of cervical wedge-shaped erosions].

The surface of single or multiple cervical wedge-shaped defects was studied with a scanning electron microscope. After an initial stage during which the root surface became smooth and polished, the developed lesions had an angular shape with the presence of one or several grooves of 0.2 to 0.3 mm in width at the angle vertex. The presence of these grooves forming horizontal gutters strongly suggested the existence of a horizontal brushing movement. Beside these large grooves, a more or less parallel network of fine striae was observed. The lesion surfaces consisted of dentin with obliquely oriented tubules which were not completely sclerosed. Relatively thin bacterial layers were present on these surfaces. The presence of horizontal wear gutters seemed to confirm the traumatic origin of the wedge-shaped defects connected with toothbrushing.

Adult↗
PubMed1987

[From phonocardiography to phonoanalysis].

We report on a new system for the examination and presentation of heart sounds, the phonoanalysis (PHA). It gives automatically a complete, objective physically founded picture of heart sounds and murmurs by registering the frequency spectrum graphically, as well as presenting in a numeric format, as a whole and as a function of time; in addition, the usual phonocardiographic and electrocardiographic leads may be obtained. A further function is to measure--probably for the first time--quantitatively the "roughness" of heart murmurs. This factor is also essential for the quality of murmurs and independent of the pitch. Therefore, the quantitative assessment of roughness has been proposed as an essential part of the physically founded description of heart murmurs in the auscultation, in addition to the determination of the dominating frequency (pitch). The term 'roughness' should not been confined to the extremely rough low-pitched heart murmurs e.g. in typical aortic stenosis. The PHA gives a better insight into the hemodynamic basis of heart murmurs and discloses properties of murmurs not recognized by auscultation and phonocardiography. The PHA can also be used for the examination of vascular, lung, bronchial and abdominal murmurs and also in connection with a stethoscope using an airborne sound microphone.

Computers↗
PubMed1986

Artifacts in dilution pharmacokinetic models caused by adherent bacteria.

Liquid cultures of a Pseudomonas aeruginosa strain in Mueller-Hinton broth diluted at rates higher than the bacterial growth rate showed the expected decrease in CFU only for 1 to 2 h. Later the CFU started to increase. This phenomenon can be explained by a hypothesis that assumes that the bacteria multiply in two different compartments. From the first compartment, which comprises bacteria homogeneously distributed in the broth, cells are eliminated at a rate that is dependent on the dilution and growth rates. Concomitantly, the second compartment is formed as a nondilutable adherent population on the surface of the culture vessel. Eventually, only cells stemming from that population appeared in the medium and were subsequently diluted. This hypothesis can be described mathematically by a linear combination of two exponential functions. The calculated values fit the experimental data well. Because similar CFU versus time curves were also found with other strains, care should be taken in interpreting results of experiments performed in liquid cultures and evaluated in terms of CFU. One should bear in mind that within a liquid culture an adherent population may exist, which differs in size according to selective influences (dilution, addition of antibiotics, etc.). This may give rise to artificial and unexpected results.

Adhesiveness↗
PubMed1985

Investigations on the bactericidal activity of fosfomycin using the membrane filter-agar dilution method and the time-kill technique.

Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) for a 99% and a 99.9% kill can be reproducibly determined for fosfomycin by the agar dilution procedure when placing the inoculum on top of membrane filters. In 88.7% (85%) of 80 bacterial strains (Enterobacteriaceae, Pseudomonas aeruginosa, Staphylococcus aureus) examined we found a 99% (99.9%) kill at concentrations higher than the respective MIC by up to one dilution step. For 5% (10%), the bactericidal concentrations were more than two steps higher. Both the MIC and the MBC were influenced by the culture medium. The influence of the medium on fosfomycin activity was also shown by the time-kill curves. In nutrient broth, Mueller-Hinton broth, Iso-Sensitest broth and human plasma water (with and without glucose-6-phosphate) we found different killing rates, different killing maxima and different times of regrowth of the cultures. The bactericidal activity of fosfomycin against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and Pseudomonas aeruginosa ATCC 27853 was more pronounced in plasma water, nutrient broth, and Mueller-Hinton broth than in Iso-Sensitest broth.

Agar↗
PubMed1985

Post-MIC effect of fosfomycin on Pseudomonas aeruginosa in vitro and in experimentally infected mice.

When two strains of Pseudomonas aeruginosa were subjected in vitro to decreasing fosfomycin concentrations in liquid cultures a half-life dependent delay of regrowth occurred after concentrations had fallen below the MIC (post-MIC effect). There was no post-MIC effect at the short half-lives corresponding to those normally found in mice. However, in similar experiments with surface cultures a post-MIC effect could also be demonstrated at short half-lives. No post-MIC effect, with reference to serum concentrations, could be found in mice infected with the same strains either in a septicaemia or infected thigh model.

Animals↗