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E Hess

Publications and source records attributed to E Hess.

At least 19 recordsLinked to original sources
PubMed2002

Synthesis of 2-[18F]fluoro-L-tyrosine via regiospecific fluoro-de-stannylation.

2-[18F]Fluoro-L-tyrosine is a fluorine labelled amino acid, known to be incorporated into newly synthesised proteins, rendering it a potentially suitable tracer to image protein metabolism in vivo using positron emission tomography. For the electrophilic preparation of 2-[18F]fluoro-L-tyrosine three protected 2-trialkylstannyl tyrosine derivatives have been synthesised for the first time as precursors. While O,N-di-Boc-2-triethylstannyl-L-tyrosine ethylester has proved to be suitable as precursor for radiosynthesis, imidazolidinon-derivatives of 2-triaklylstannyl tyrosine have not because of difficult fast hydrolysis of a phenolic O-methyl protective group. The di-Boc-tin derivative of tyrosine ethylester readily reacted with [18F]F2, which was prepared via the 18O(p,n)18F nuclear reaction. 2-[18F]Fluoro-L-tyrosine was isolated after full deprotection with aqueous hydrobromic acid and HPLC purification with activities of 1.41 +/- 0.32GBq. The isomeric and enantiomeric purity is high (both >99%). The preparation procedure is facile and easy to automate. The chemical yields of this fluoro-de-stannylation reaction as well as of the synthesis of 6-[18F]fluoro-L-dopa, determined with an analogous precursor and non-radioactive fluorine under identical conditions, amounted to 42.7 +/- 1.6% and 60.2 +/- 2.8%, respectively.

Journal Article↗
PubMed2001

Activation of the dienophilicity of indoles in normal electron demand [4 + 2] cycloadditions under high pressure.

[reaction: see Text] Activation by either high pressure or a combination of Lewis acid catalysis and high pressure allows indole derivatives to behave as dienophiles in [4 + 2] cycloaddition reactions under mild conditions. The biactivation mode has the highest impact on the stereoselectivity of the reaction. The cycloadducts resulting from these reactions are characterized by boat-shape conformations that bear well-defined orthogonal planes.

Journal Article↗
PubMed2001

In vitro production of antibodies to histones in patients receiving chronic procainamide therapy.

OBJECTIVE: Procainamide related autoimmunity is characterized by the production of antibodies to histones and, in particular, to the H2A-2B dimer. We evaluated in vitro production of antibodies to total histones and the H2A-2B dimer by peripheral blood mononuclear cells (PBMC) from patients chronically exposed to procainamide and related this to in vivo production, and assessed possible immunostimulatory response by the postulated reactive metabolite procainamide hydroxylamine (PAHA) using PAHA conjugated autologous erythrocytes. METHODS: We evaluated in vitro spontaneous and mitogen induced production of histone antibodies by PBMC from 26 asymptomatic patients, who were chronically receiving procainamide, in the presence and absence of PAHA conjugated autologous erythrocytes. Correlations with in vivo production were sought. RESULTS: PBMC from 9 patients revealed significant spontaneous production of histone antibodies, of whom 2 developed procainamide related lupus within 2 mo of the evaluation. There was a significant increase in in vitro production of antibodies to total histones by PBMC that had been cultured in the presence of PAHA-autologous erythrocyte conjugates, but in the absence of mitogens, from 15 (65%) of 23 patients, and of antibodies to H2A-2B by cells from 10 (42%) of 24 patients. Patients' cells that were co-cultured with PAHA-erythrocyte conjugates produced significantly greater amounts of antibodies to both total histones (p = 0.03) and the H2A-2B dimer (p = 0.009) compared with those cultured alone. Co-culture with similarly pretreated erythrocytes also resulted in a significant increase in the production of antibodies to total histones (p < 0.001), but not to the H2A-H2B dimer, by cells from controls. CONCLUSION: Some patients receiving chronic procainamide therapy have spontaneous production of histone antibodies. Co-culture with PAHA-erythrocyte conjugates resulted in significantly greater production, suggesting an immunomodulating effect by this metabolite.

Adult↗
PubMed2000

Improved target system for production of high purity [18F]fluorine via the 18O(p,n)18F reaction.

An improved aluminium target system for production of elemental fluorine via the 18O(p,n)18F reaction using a two-step irradiation protocol is described. In the first step highly enriched gaseous oxygen-18 is irradiated with protons to form fluorine-18 which gets deposited on the inner target surface. In the second step, after cryogenic recovery of oxygen-18 target gas, a mixture of elemental 'cold' fluorine and krypton is introduced and a short proton irradiation is done, whereby an isotopic exchange between the gaseous fluorine and the deposited radiofluorine occurs. The second step leads to the recovery of the radiofluorine as [18F]fluorine. Optimisation studies were performed regarding the yield and specific radioactivity of [18F]fluorine. Furthermore, some irradiation parameters relevant to the recovery step were investigated. It was found that a 15 to 20 min irradiation with a beam current of 20 microA is sufficient for the isotopic exchange between the fluorine-carrier and the 18F-radioactivity deposited on the inner wall of the target. The distribution of the 18F-radioactivity deposited on the inner target surface is inhomogeneous, probably due to convection effects. Extensive radioanalytical techniques were applied to characterise the reactivity of [18F]fluorine and to identify undesired nonreactive 18F-compounds, mainly [18F]tetrafluoromethane and [18F]nitrogentrifluoride. The [18F]fluorine produced in the system used has the distinction of having a negligible contamination from those inert 18F-compounds. This is a combined effect of the use of highest purity gases and a welded target construction, which avoids any contact of the gases with organic material during irradiations. The target has proved to be very reliable for production of [18F]fluorine in high yields of up to 34 GBq and specific activities of 350-600 GBq/mmol, both at 30 min after end of activation bombardment.

Aluminum↗
PubMed1999

Acute and long-term stability studies of deoxy hemoglobin and characterization of ascorbate-induced modifications.

The reaction of ascorbate with recombinant hemoglobin (rHb1.1) in the presence of differing partial pressures of oxygen was studied. In the presence of 15 000 ppm (1.5%) residual oxygen, ascorbate/oxygen-mediated reactions resulted in an increased rate of autoxidation, modification of the beta-globin, increased oxygen affinity and decreased maximum Hill coefficient. One of the observed modifications to the beta-globin was a 72 Da addition to its N-terminus. Detailed characterization indicates the modification was an imidazolidinone type structure. Thorough deoxygenation of the hemoglobin solution to <150 ppm of oxygen prior to addition of ascorbate was required to prevent these modifications. Addition of ascorbate to the deoxy hemoglobin (deoxyHb) at pH 8 induced aggregation, eventually leading to precipitation. No such precipitation was observed at pH 7. Long-term storage of the hemoglobin was carried out by addition of ascorbate to deoxyHb at pH 7. The level of methemoglobin remained at <2% for up to 1 year at 4 degreesC, with no detectable precipitation of the protein. Modifications similar to those observed by the acute studies were observed over the 1-year period and correlated with disappearance of the added ascorbate.

Ascorbic Acid↗
PubMed1999

Acetylation status is associated with serological changes but not clinically significant disease in patients receiving procainamide.

OBJECTIVE: Autoantibodies occur in the majority of patients receiving procainamide (PA) for more than one year. Slow acetylator status has been proposed to predispose to their development. We previously reported the results of serological evaluation of 52 asymptomatic patients receiving PA. The aims of this study were to follow these patients to determine the incidence of drug related lupus (DRL) and serologic changes in patients receiving longterm PA therapy; and to evaluate the possible effect of acetylator status on the development of PA autoimmunity. METHODS: Fifty-two patients receiving PA were reevaluated after a mean of 31.5 months. Antinuclear antibodies and antibodies to histones, dsDNA, and polyadenylic acid (PolyA) were assayed. Acetylator status was determined by phenotyping and genotyping methods. Five additional patients referred with a diagnosis of DRL were also evaluated. RESULTS: Autoantibodies were detected in the majority of patients still receiving PA and in some patients in whom PA had been discontinued. Slow acetylator status correlated with IgG antibodies to the H2A-2B dimer complex. Acetylator status did not correlate with PA dose. Seven of the 9 patients with PA related lupus were fast acetylators. CONCLUSION: Most patients receiving PA have autoantibodies that may persist after discontinuation of PA. Despite persistently high frequency of autoantibodies the majority of these patients did not develop DRL. Slow acetylator status correlated with IgG antibodies to H2A-2B but was not a risk factor for the development of PA related lupus.

Acetylation↗
PubMed1997

Incorporation of norvaline at leucine positions in recombinant human hemoglobin expressed in Escherichia coli.

We report here a novel finding that norvaline can be incorporated in place of leucine in recombinant human hemoglobin expressed in Escherichia coli. The presence of the norvaline was confirmed by several analytical methods such as amino acid analysis, peptide mapping, electrospray mass spectrometry, and Edman protein sequencing. It appears that substitution is distributed across both the beta- and di-alpha-globins in purified recombinant hemoglobin. The level of misincorporation correlated with the ratio of the free norvaline/leucine pool available in the cell culture. This suggests that the incorporation of norvaline for leucine occurs through misaminoacylation of tRNALeu, similar to the misincorporation of norleucine for methionine found in many recombinant proteins expressed in E. coli.

Amino Acid Sequence↗
PubMed1997

Mapping of recombinant hemoglobin using immobilized trypsin cartridges.

A tryptic mapping procedure has been developed for a recombinant hemoglobin (rHb1.1) using an immobilized trypsin cartridge. Apohemoglobin is passed through the trypsin cartridge and the products of the digestion are captured directly onto an in-line C18 reversed-phase column. The peptides are then separated using a gradient elution. This new procedure is rapid and reproducible and can be fully automated. The total time of analysis is less than 2 h. The mapping of apohemoglobins produced an unexpected isomerization of two peptides: beta8,9 (K66-K82) and alpha8,9 (K61-K90). It appears that the isomerization may occur through transpeptidation followed by proteolysis at a newly generated site next to the site of ligation. This mapping procedure can be a useful tool for research and routine analysis of proteins.

Amino Acid Sequence↗
PubMed1994

Tripartite differentiation in a carcinoma of the duodenum.

BACKGROUND: Carcinomas containing three distinctly different cell lines have been encountered in the colon and rectum, but a tripartite malignancy in the small intestine has not been reported previously. METHODS: A duodenal carcinoma was studied by light and electron microscopic examination and immunohistochemistry. RESULTS: The duodenal carcinoma was found to have tripartite glandular, squamous, and neuroendocrine differentiation. Histologically, an adenocarcinoma, which originated in a villous adenoma, was continuous with squamous cell carcinoma and small cell carcinoma components. Tumor cells of the squamous cell carcinoma component had conspicuous intercellular bridges but did not form keratin pearls. Immunohistochemical analysis showed strong expression of carcinoembryonic antigen (CEA) by the adenocarcinomatous component. The squamous cell carcinoma component demonstrated focal weak CEA and neuron specific enolase (NSE) reactivity. Ultrastructurally, tumor cells of this component had frequent desmosomes and free tonofilaments. The small cell carcinoma had clusters of dense core granules in tumor cell cytoplasmic processes, which are indicative of neuroendocrine differentiation. This neuroendocrine component was immunoreactive for somatostatin and NSE. CONCLUSIONS: This case of tripartite duodenal carcinoma supports the theory of an origin from an intestinal pluripotential stem cell capable of differentiating into multiple cell types.

Adenocarcinoma↗
PubMed1989

Spectral sensitivity, absolute threshold, and visual field of two tick species, Hyalomma dromedarii and Amblyomma variegatum.

1. The spectral sensitivity in the wavelength range of 340-750 nm was determined by both a behavioral approach based on spontaneous positive phototaxis and the electroretinogram (ERG). 2. Concerning phototaxis the camel tick, Hyalomma dromedarii, showed two sensitivity maxima, one in the UV range (ca. 380 nm) and another in the blue-green range (ca. 500 nm). At higher intensities the relative sensitivity was more pronounced in the UV and at lower intensities more pronounced in the blue-green (reverse Purkinje shift). In the tropical bont tick, Amblyomma variegatum, there was a single sensitivity maximum in the blue range (ca. 480 nm). 3. In the ERG there was a maximum in the blue range (ca. 470 nm) in both species and a weak secondary maximum in the UV in Hyalomma. 4. The absolute sensitivity was very high. The threshold irradiance of phototaxis was as low as 5.2 x 10(6) photons.s-1.cm-2 in Hyalomma and 5.2 x 10(8) photons.s-1.cm-2 in Amblyomma. 5. When the eyes of Hyalomma were covered, the threshold irradiance was still very low, namely 5.2 x 10(8) photons.s-1.cm-2, indicating high absolute sensitivity of the extraretinal photoreceptors. 6. The visual field of the eyes was determined by ERG measurements. In both species the optical axis of each eye, i.e., the center of the visual field, was directed somewhat to the side and above the horizon. In Hyalomma this direction was 35 degrees to the long axis of the animal and 30 degrees above the horizon for natural body posture during walking. In Amblyomma the corresponding angles were 39 degrees and 33 degrees, respectively. The size of the field (at 50% sensitivity) in Hyalomma was relatively small, namely 14 degrees in the horizontal and 25 degrees in the vertical direction, compared with that of Amblyomma with 43 degrees and 49 degrees, respectively. 7. This is the first demonstration in ticks of spectral and absolute sensitivity by the behavioral approach and of the visual field by ERG. The results suggest that tick eyes possess features of both spider eyes and insect ocelli.

Animals↗
PubMed1988

Drug-related lupus.

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Antibodies, Antinuclear↗
PubMed1986

Field tests of the response of female Amblyomma variegatum (Acari:Ixodidae) to the synthetic aggregation-attachment pheromone and its components.

Fifty percent of an Amblyomma variegatum female population were able to find upwind-positioned targets containing the synthetic aggregation-attachment pheromone of this species or the pheromone component o-nitrophenol alone. The ticks were not attracted to the other components of the pheromone: methyl-salicylate and pelargonic acid. The mean time required for the ticks to reach a target at 1 m from the starting point was 3 min and 20 s.

Animals↗
PubMed1980

Ultrastructural study of the tetrathyridium of Mesocestoides corti Hoeppli, 1925: tegument and parenchyma.

The study of dividing and non-dividing tetrathyridia using electron microscopy shows that the mode of multiplication by antero-posterior fission of these larvae is due to a particular tissue which is called the "apical massif". The apical massif is a part of the tegumental syncytium. It is located at the top of the scolex. It represents a polynucleated cell mass which has cytomorphogenetic power. During asexual multiplication, it differentiates into tegumental syncytium, sub-tegumental muscles, glycogen-storing parenchyma cells, and other cell types. Parts of it remain undifferentiated. The hypothetic origin of the apical massif is discussed. Longitudinal growth of the tetrathyridia occurs by invasion of migrating cells into the tegumental syncytium. These cells also originate from the apical massif. During asexual multiplication and longitudinal growth, filamentous microtriches are synthesized below the plasmalemma of the superficial cytoplasm of the tegumental syncytium. It is supposed that the blade-like microtriches derive from filamentous forms.

Animals↗