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Biomedical subjects

A Buchholz

Publications and source records attributed to A Buchholz.

At least 19 recordsLinked to original sources
PubMed2001

Quantification of intracellular metabolites in Escherichia coli K12 using liquid chromatographic-electrospray ionization tandem mass spectrometric techniques.

The quantitative comprehension of microbial metabolic networks is a prerequisite for an efficient rational strain improvement ("metabolic engineering"). It is therefore necessary to accurately determine the concentration of a large number of reactants (i.e., metabolites, nucleotides, cofactors) in order to understand "in vivo" reaction kinetics. Quantification of intracellular concentrations of glycolytic intermediates and nucleotides in Escherichia coli K12 using a perchloric acid extraction and an LC-ESI-MS method was achieved. Intracellular metabolites (e.g., glucose 6-phosphate, fructose 1,6-bisphosphate, 6-phospho gluconate, acetyl-CoA, adenine nucleotides) were quantified under defined (glucose-limited steady-state) growth conditions. The method was verified by comparing the intracellular metabolite concentrations measured via LC-ESI-MS with enzymatic determinations. It is thus possible to identify and quantify more than 15 intracellular metabolites in parallel with a minimal amount of sample volume.

Acetyl Coenzyme A↗
PubMed2001

Investigation of sodium cations in dehydrated zeolites LSX, X, and Y by 23Na off-resonance RIACT triple-quantum and high-speed MAS NMR spectroscopy.

We investigated by two-dimensional 23Na ORIACT MQMAS NMR and one-dimensional 23Na high-speed MAS NMR spectroscopy a homologous series of dehydrated zeolites with faujasite structure. The framework silicon to aluminum ratios varied between 1.06 and 2.60. In the case of zeolites Y (nSi/nAl = 2.60), we studied materials with sodium exchange degrees between 0 and 95%. The recently introduced ORIACT method (Caldarelli, S.; Ziarelli, F. J. Am. Chem. Soc. 2000, 122, 12015) significantly improved the resolution of the MQMAS spectra, in comparison with earlier studies. It was thus possible to extract meaningful quadrupole parameters by MQMAS NMR, which were used as a starting point for the simulation of 1D MAS NMR spectra to obtain more accurate values of the NMR parameters and site occupancy. We were able to show by this approach that in zeolite NaLSX the SI positions in the hexagonal prisms are occupied by sodium cations. For the homologous series of zeolites Y, it was found that sodium cations located at SII positions are the easiest to be substituted by ammonium ions through the exchange process.

Journal Article↗
PubMed2001

Effects of temperature and concentration of the accelerators ethoxylated alcohols, diethyl suberate and tributyl phosphate on the mobility of [14C]2,4-dichlorophenoxy butyric acid in plant cuticles.

Intrinsic activities of monodisperse ethoxylated dodecanols (MEDs), diethyl suberate (DESU) and tributyl phosphate (TBP) were investigated using Stephanotis floribunda leaf cuticular membranes (CMs) and [14C]2,4-dichlorophenoxy butyric acid (2,4-DB) as a model solute. When sorbed in cuticular membranes, MEDs, DESU and TBP increase solute mobility and are called accelerators for this reason. With MEDs, dose-effect curves (log mobility vs accelerator concentration) were linear but, with DESU and TBP, curves convex to the x axes were obtained that approached a maximum at 90 and 150 g kg-1, respectively. Accelerators increased the mobility of 2,4-DB in the CMs by 9- to 48-fold, and effects were larger at lower temperatures (range 15-30 degrees C). Activation energy for diffusion of 2,4-DB was 105 kJ mol-1, decreasing with increasing accelerator concentrations to 26 kJ mol-1 with DESU at 90 g kg-1 and 64 kJ mol-1 with TBP at 150 g kg-1. Thus, the intrinsic activity of DESU was much higher than that of TBP, which implies that, for a given effect, less DESU than TBP would be needed. MEDs were also very effective accelerators, lowering activation energies to 36 kJ mol-1. Data are discussed in relation to increasing rates of foliar penetration of active ingredients at low temperatures.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

Thermodynamic analysis of diffusion of non-electrolytes across plant cuticles in the presence and absence of the plasticiser tributyl phosphate.

Solute mobility in cuticular membranes (CMs) of 14 plant species (Citrus aurantiumn L., Citrus grandis L., Hedera helix L., Ilex aquifolium L., Ilex paraguariensis St.-Hil., Malus domestica Borkh. cv. Golden Delicious, Populus alba L., Prunus laurocerasus L., Pyrus communis L. cv. Bartlett, Conference and Gellerts Butterbirne, Pyrus pyrifolia (Burm. f.) Nakai, Schefflera actinophylla (Endl.) Harms and Strophanthus gratus Baill.) was measured over the temperature range 25-55 degrees C. The five organic model compounds differed in size (130-349 cm3 mol(-1)) and cuticle/water partition coefficient (18-10(8)). For all individual CMs (n = 297), the data were plotted according to the thermodynamic relationship between the preexponential factor (which is proportional to entropy) of the Arrhenius equation and the activation energy (enthalpy) of diffusion (ED). A strict linear correlation was obtained, providing evidence that the five compounds diffused along the same lipophilic diffusion path in all plant species tested. Extracting cuticular waxes from CMs of four plant species (Hedera, Pyrus, Schefflera and Strophanthus) had no effect on the slope of the plot but a parallel displacement towards higher entropy was observed with these polymer matrix (MX) membranes. This displacement is interpreted as a temperature-independent tortuosity factor directly related to entropy. The influence of the plasticiser tributyl phosphate on solute mobility at various temperatures was measured for CM and MX membranes. The plasticiser increased solute mobility and ED was reduced drastically for both membrane types. This plasticiser effect was almost completely reversible, when tributyl phosphate was desorbed from the membranes. For both, plasticised CM and MX, the thermodynamic correlation exists whereby all data points lie on the same line. The data are used to characterise the lipophilic pathway across plant cuticles in terms of the free-volume theory.

Diffusion↗
PubMed1990

Inhibition of low Km cyclic GMP phosphodiesterases and potentiation of guanylate cyclase activators by cicletanine.

Cicletanine is an antihypertensive/vasorelaxant/natriuretic agent of unknown mechanism. We wished (a) to determine if cicletanine interacts with guanylate cyclase activators that modulate vasomotor tone and sodium balance [i.e., atriopeptin II (AP II), endothelium-derived relaxing factor (EDRF), and sodium nitroprusside (SNP)], and (b) to define the subcellular basis for this interaction by quantitating the effects of cicletanine on low Km cyclic GMP phosphodiesterase (PDE) activity. In phenylephrine-contracted rat aortic smooth muscle, the vasorelaxant potency of cicletanine was increased twofold in the presence of a threshold-relaxant concentration of AP II, and functional cyclic GMP PDE inhibition was also evident from the three- to sixfold potentiation by cicletanine of AP II- or SNP-induced vasorelaxation. Vasorelaxation produced by cicletanine was not endothelium dependent, however. In further studies, intravenous (i.v.) administration of cicletanine or the low Km cyclic GMP PDE inhibitor, zaprinast, decreased blood pressure (BP) greater than or equal to 20% in conscious spontaneously hypertensive rats (SHR). These results are consistent with the additional finding that cicletanine inhibited Ca2(+)-calmodulin (CaM) cyclic GMP PDE and zaprinast-sensitive cyclic GMP specific PDE over a concentration range (10-600 microM) similar to that for vasorelaxation. Thus, inhibition of low Km cyclic GMP PDEs by cicletanine may be partly responsible for the vasorelaxant effect of cicletanine as well as the potentiation by cicletanine of the vasorelaxant actions of guanylate cyclase activators. The extent to which this mechanism contributes to the antihypertensive efficacy of cicletanine has not yet been fully determined.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

[An unusual benign hamartomatous tumor of the lung].

About a rare benign tumor of the lung of a fifty-nine years old woman is reported. The possible relation to the group of the pulmonary hamartomas is discussed. The tumor was benoted as "Benign angiohamartomatous tumor".

Endothelium, Vascular↗
PubMed1990

[Mullerian adenosarcoma].

The Müllerian adenosarcoma is an extremely rare entity of tumours of the group of the Müllerian and mesodermal mixed tumours. This tumour seems to be a malignant transformation of the uterine papillary cystadenofibroma. The periglandular malignant transformation of the stromal component and the benign glandular structures are typical signs of the Müllerian adenosarcoma. In accordance with references the prognosis of the adenosarcoma is better than those of other Müllerian mixed tumours. The demonstrated cases warn against undervalue.

Aged↗
PubMed1990

[Struma ovarii. Short report of 2 cases].

A 75-year old and a 48-year old woman were treated by hysterectomy and unilateral adenectomy. The extirpated ovarian tumors both have shown histologically the structures of Struma ovarii with monodermal differentiation. The Struma ovarii represents a rare special manifestation of mature teratoma with typical histological appearance. At similarities to original thyroid tissue are given directions.

Aged↗
PubMed1989

Cell-line-dependent inhibition of phenotypic expression of preneoplastic and neoplastic tracheal epithelial cells by normal tracheal cells in denuded tracheal transplants.

The inhibitory role of normal cells on the expression of neoplastic or preneoplastic cells was investigated using repopulated, heterotopic tracheal transplants. Denuded tracheal transplants were repopulated with a constant number of cells composed of different ratios of normal and neoplastic or preneoplastic rat tracheal epithelial (RTE) cells. Tracheas were harvested at 2 and 6 weeks after implantation, and examined histologically and in cell culture for the presence of the abnormal cells. Two neoplastic cell lines showed marked differences in the number and extent of squamous cell carcinomas which developed in tracheas repopulated at equivalent ratios of RTE: neoplastic cells. One preneoplastic cell line was almost completely inhibited in proliferative and phenotypic expression by normal cells, in contrast to a marked lack of suppression by normal cells of a second preneoplastic cell line. The extent of squamous metaplasia present, or the presence of invasive squamous cell carcinoma, was dependent upon the cell line instilled, suggesting that the cell lines represent different stages in the progression toward neoplasia. The lack of inhibition of some tumorigenic or preneoplastic cells by normal cells in this study is in conflict with previously published reports which indicate that the presence of greater than 10(4) normal cells are capable of inhibiting neoplastic expression in this model. Based on these studies, it appears that the nature of the neoplastic or preneoplastic cell is critical in determining whether inhibition by normal cells can occur.

Animals↗
PubMed1989

[A membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus. 2. Substrate specificity of the enzyme].

The substrate specificity of the membrane-bound alanine aminopeptidase from Acinetobacter calcoaceticus was investigated with a series of substituted amides of alpha-amino acids. In contrast to mammalian AAP forms, the rate of hydrolysis of the AAP from Acinetobacter calcoaceticus is higher using 4-nitranilide than 2-naphthylamide substrates. The enzyme affinity is very high for alanine substrates and decreases in the series of the amide substituents, from methyl coumarylamides, 4-nitranilides, 4-methoxynaphthylamides to the 2-naphthylamides. The alanine aminopeptidase shows its highest affinity to Ala-MCA (Km = 77 mumol(s)/1).

Acinetobacter↗
PubMed1987

Use of adherence protein of Mycoplasma pneumoniae as antigen for enzyme-linked immunosorbent assay (ELISA).

Antibodies against the adherence protein of Mycoplasma pneumoniae are regularly found in patients with M. pneumoniae infection. Therefore, this 168-kilodalton (kDa) protein was used as an antigen in a dot-ELISA for serological diagnosis of M. pneumoniae disease. M. pneumoniae proteins were separated by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), gels were stained with Coomassie Blue, and the 168-kDa protein band was cut out and eluted using a special electroelution device. Isolated proteins or sonicated whole-cell antigens, respectively, were immobilized on a 96-well filtration plate with a nitrocellulose bottom (dot-ELISA). The test procedure was performed as in conventional ELISA tests, using alkaline phosphatase-labeled antihuman IgM or IgG antibodies, respectively, to detect antigen-antibody complexes. All results were confirmed by immunoblotting. The dot-ELISA using the 168-kDa antigen proved to be sensitive and specific. The specificity was tested on 53 sera of M. pneumoniae infections and on 490 serum specimens of patients with other respiratory diseases due to other pathogens, or with clinical conditions such as pancreatitis, meningitis or endocarditis. With regard to IgM antibodies, no false-positive reactions were found in non-M. pneumoniae diseases against the 168-kDa antigen, but there were such reactions against other M. pneumoniae proteins in immunoblots.

Adhesins, Bacterial↗
PubMed1986

[Cryosurgical treatment of cervical intraepithelial neoplasia following cervical smears and curettage].

65 patients exhibiting colposcopically and cytologically atypical epithelium in the cervix were treated by cryosurgery with liquid nitrogen. 63 of whom were confirmed histologically after surface scraping and curettage of the cervix. The patient then were followed cytologically and colposcopically 8 and 12 weeks after cryosurgery. According to that the definitive histological diagnosis was performed after conization (48 patients) hysterectomy (12 patients) and surface scraping and curettage of the cervix (8 patients). Colposcopical, cytological and histological findings after surface scraping of the cervix showed a correlation rate in the 95% range. Treatment failure rate following cryosurgery showed an increased percentage with increased grade of CIN. A complete destruction of ectocervical pathologic tissue in CIN 1 and 2 is opposed to a persistent disease rate of 20 percent in patients with CIN 3. The failure rate was significantly higher in cases without fully visualization of squamocolumnar junction. Cytological follow-up predicted all cases with histologic diagnosis of persistent disease. Colposcopical evaluation was frequently unsatisfactory after cryosurgery. Cryosurgery of CIN should be reserved for the treatment of those patients in whom the criteria for patient selection are performed and the benefits of this method outweigh the possible drawbacks.

Carcinoma in Situ↗