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L Witte

Publications and source records attributed to L Witte.

70 records · Page 4Linked to original sources
PubMed1989

Characterization of a meta-Fluorotyrosine-Tolerant Cell Culture of Eschscholtzia californica Cham.

A cell line of Eschscholtzia californica selected for meta-fluorotyrosine (MFT) tolerance was found to have 10-fold increased levels of phenylalanine and tyrosine compared to the parent line, while most other amino acids were only increased 2-fold. Tracer experiments with shikimic acid in the presence of MFT showed that the biosynthesis of the aromatic amino acids was not impaired in the tolerant line. Feeding experiments with phenylalanine, tyrosine, or shikimic acid also revealed a reduced turnover of the pools of the aromatic amino acids in the variant. Thus undisturbed de novo biosynthesis of the aromatic amino acids and dilution of toxic effects of MFT by the enlarged pool sizes seemed to be the main reason for the acquired tolerance. Despite the enlarged availability of the precursor tyrosine, formation of the benzophenanthridine alkaloids was enhanced neither in the growth nor in the production medium.

Journal Article↗
PubMed1988

Effect of potassium supplementation combined with dietary sodium reduction on blood pressure in men taking antihypertensive medication.

It has long been suspected that sodium and potassium intake influence blood pressure. Since both these electrolytes can be modified by diet, attention has focused on decreasing sodium intake and increasing potassium intake as a potential way of treating and preventing hypertension. Several short-term controlled clinical trials have examined the effect of supplemental potassium intake on blood pressure, but with inconsistent results. The Minnesota Mount Sinai Hypertension Trial (MSHT) is a double-blind study comparing placebo with potassium supplementation for controlling blood pressure in hypertensive men on a sodium-restricted diet over a 2-3 year follow-up period. At the time of randomization to placebo or supplemental potassium and through 12 weeks of follow-up, the patients were taking antihypertensive medication. This preliminary report compares blood pressure changes between the placebo and supplemental potassium groups over the first 12 weeks of the trial.

Antihypertensive Agents↗
PubMed1985

Phosphorus-31 nuclear magnetic resonance investigation of the in vivo regulation of intracellular pH in cell suspension cultures of Nicotiana tabacum: the effects of oxygen supply, nitrogen, and external pH change.

31P NMR was used to study the in vivo response of intracellular phosphorus-containing compounds of cell suspension cultures of Nicotiana tabacum to extracellular events. Limitation of the oxygen supply in a static system (sealed tube) caused a strong pH decrease of the cytoplasm and a smaller fall in the vacuolar pH. The rate of this process was independent of the age of the cells, except for those at the end of the growth cycle where either reserve supplies of inorganic phosphate have been depleted or metabolism has ceased. The cells can be returned quickly to their normal pH and metabolic status by reoxygenation after depletion times as long as 4.5 h. Regassing with N2 after anaerobiosis also caused the return of the nearly normal pH status, which indicates that rapid cell acidification is caused almost entirely by CO2 accumulation. In a second type of anaerobiosis, attained by continual passage of N2, cytoplasmic pH fell only slowly to a constant value higher than in the static case. Here acidification appeared to arise, at least in part, from lactate accumulation. Provided aeration occurred, the cytoplasm was maintained at a constant pH of 7.5 +/- 0.1 for changes in the medium pH value between 6.5 and 3. The biochemical and biotechnological implications of these results are discussed.

Cell Cycle↗
PubMed1984

Formation and identification of interfacial-active glycolipids from resting microbial cells.

Resting cells of Arthrobacter sp. strain DSM2567 incubated in the presence of various mono-, di-, or trisaccharides biosynthesized different glycolipids. All eight glycolipids, containing the corresponding carbohydrate moiety and one, two, or three alpha-branched beta-hydroxy fatty acids, were produced when mannose, glucose, cellobiose, maltose, and maltotriose were used as carbon sources in a simple phosphate buffer. The structures of the compounds were elucidated by means of H and C nuclear magnetic resonance spectroscopy and by chemical ionization mass spectroscopy. In high-salinity solution, the substances showed different surfactant properties. Cellobiose and maltose monocorynomycolates reduced the interfacial tension from 42 to 1 mN/m at critical micelle concentrations below 20 mg/liter.

Journal Article↗
PubMed1984

Functional outcome of closed head injury in children and young adults.

A comprehensive questionnaire which measured gross and fine motor function in the area of cognition, communication, and social development was completed by parents of children and young adults who had suffered severe closed head injuries between the years 1967 and 1978. The final sample included 42 returned questionnaires. Of these patients, 15 (37%) were considered independent, 20 (49%) dependent, and 6 (14%) had died. The area of cognition and communication dysfunction seemed to contribute most to dependency. The younger age group and the patients who were comatose for a shorter period of time tended to do the best functionally. While severe closed head injury can result in significant disability, many patients can achieve functional independence.

Adolescent↗
PubMed1979

Studies on cytochrome c oxidase, VII. Isolation and chemical characterization of polypeptide VII.

Polypeptide VII of cytochrome c oxidase was isolated and purified by gel filtration on Bio-Gel P-10 in 10% acetic acid. Automatic Edman degradation of this peptide chain was not successful, because it is blocked at the N-terminus. The amino acid analysis shows a relatively high content of hydrophilic residues (54%). On the basis of this analysis and the apparent molecular weight by sodium dodecyl sulfate gel electrophoresis and gel filtration, a chain length of about 80 residues was calculated. Among the tryptic peptides one blocked heptapeptide was found. Cleavage of this peptide with thermolysin gave two peptide fragments, one of which was not retained on a cation exchange resin. Mass spectrometric sequence determination of this peptide revealed the structure Ac-Ala-Glu-Asp for the N-terminus of polypeptide VII. Treatment with carboxypeptidase A at two different pH values showed that the C-terminal amino acid is isoleucine and the penultimate amino acid is lysine.

Amino Acid Sequence↗
PubMed1977

Quantitative analysis of trifluoroacetic acid in body fluids of patients treated with halothane.

A simple procedure for the quantitative analysis of trifluoroacetic acid (TFA) in urine and serum from patients narcotized with halothane is described. This involves addition of sodium hydroxide to the body fluid, evaporation of the aqueous phase and esterification of TFA in concentrated sulphuric acid with 2,2,2-trichloroethanol. The gaseous phases above the reaction mixture were then analyzed by gas chromatography with a nickel-63 electron-capture detector. The detection limit was 1 microgram of TFA per mililitre of body fluid (200 microgram of body fluid are analysed) and the relative standard deviation was +/-6%. Patients treated with ethrane, another commercial anaesthetic, did not produce any detectable TFA.

Anesthesia↗
PubMedDate not supplied

Chemical and physical characterization of four interfacial-active rhamnolipids from Pseudomonas spec. DSM 2874 grown on n-alkanes.

Four extracellular glycolipids produced under growth-limiting conditions were isolated from the culture broth of Pseudomonas spec. DSM 2874. After purification by column and thick-layer chromatography they were identified as anionic rhamnolipids. 1H and 13C-NMR studies showed that two of these, beta(beta(2-O-alpha-L-rhamnopyranosyloxy)decanoyl)decanoic acid and beta(beta(2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosylox y)decanoyloxy) decanoic acid, were identical with compounds described previously, while the other more hydrophilic compounds, beta(2-O-alpha-L-rhamnopyranosyloxy)decanoic acid and beta(2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyloxy) decanoic acid, were new compounds. Surface and interfacial activity of the organic crude extract and of the purified components were determined in different aqueous solutions. The pH-dependence of surface and interfacial properties of the two previously described rhamnolipids (4, 20, 23) were examined in Teorell-Stenhagen-buffer (supplemented with 10% NaCl) at pH 3.0 and pH 9.0. All rhamnolipids reduced the surface-tension from 72 to about 30 mN/m and the interfacial-tension from 42 to about 1 mN/m. The critical micelle concentrations were of the order of 5 to 200 mg/l depending on the structure of the molecule.

Alkanes↗
PubMedDate not supplied

Antibiotic and cytotoxic activity of brominated compounds from the marine sponge Verongia aerophoba.

Analysis of the marine sponge Verongia aerophoba from the Canary Islands afforded eight brominated secondary metabolites including the small molecular weight compounds aeroplysinin-1 (5) and the dienone (7) which were previously shown to arise by enzymatically catalyzed degradation of aerophobin-2 (4) and isofistularin-3 (1) following breakdown of the cellular compartmentation of the sponge. All compounds were identified from their NMR and mass spectra. Aeroplysinin-1 as well as dienone which arise from isofistularin-3 or aerophobin-2 by biotransformation within the sponge showed a significantly higher antibiotic as well as cytotoxic activity than their biogenetic precursors. Antibiotic activity was studied with respect to several gram-positive and gram-negative bacteria including B. subtilis, S. aureus and E. coli. The MICs (MBCs) of aeroplysinin-1 (5) and the dienone (7) varied between 12.5-25 (50-100) micrograms/ml respectively. Cytotoxicity was tested in vitro towards HeLa cells, a human cervix uteri tumour cell line. Aeroplysinin-1 (5) and the dienone (7) displayed pronounced cytotoxic activity with IC50s of 3.0 and 3.2 microM respectively. A five-fold increase in cytotoxicity was observed after O-acetylation of the dienone (7). The IC50 of the dienone O-acetate (0.6 microM) was comparable to that of the clinically used anticancer drug cisplatin (0.7 microM).

Animals↗
PubMedDate not supplied

Bioactive alkaloids from the tropical marine sponge Axinella carteri.

Analysis of the tropical marine sponge Axinella carteri afforded six unusual alkaloids, including the new brominated guanidine derivative 3-bromo-hymenialdisine. The structure elucidation of the new alkaloid is described. The alkaloid patterns of sponges collected in Indonesia or in the Philippines were shown to be qualitatively identical suggesting de novo synthesis by the sponge or by endosymbiontic microorganisms rather than uptake by filter feeding. All alkaloids were screened for insecticidal activity as well as for cytotoxicity. The guanidine alkaloids hymenialdisine and debromohymenialdisine exhibited insecticidal activity towards neonate larvae of the polyphagous pest insect Spodoptera littoralis (LD50s of 88 and 125 ppm, respectively), when incorporated into artificial diet and offered to the larvae in a chronic feeding bioassay. The remaining alkaloids, including the new compound were inactive in this bioassay. Cytotoxicity was studied in vitro using L5178y mouse lymphoma cells. Debromohymenialdisine was again the most active compound (ED50 1.8 micrograms/ml) followed by hymenialdisine and 3-bromohymenialdisine, which were essentially equitoxic and exhibited ED50s of 3.9 micrograms/ml in both cases. The remaining alkaloids were inactive against this cell line.

Alkaloids↗
PubMedDate not supplied

Bioactive terpenes from the soft coral Heteroxenia sp. from Mindoro, Philippines.

A marine soft coral species of the genus Heteroxenia collected from Mindoro Island, Philippines yielded two cadinene sesquiterpenes, (+)-alpha-muurolene (1) and a novel derivative (+)-6-hydroxy-alpha-muurolene (2), as well as the biologically active polyhydroxysterol, sarcoaldosterol A (3). The structure of the novel compound was unambiguously established on the basis of NMR spectroscopic (1H, 13C, COSY, 1H-detected direct and long range 13C-1H correlations) and mass spectrometric (EIMS) data. All compounds were active against the phytopathogenic fungus Cladosporium cucumerinum. The isolated terpenes were also active in the brine shrimp lethality test.

Animals↗
PubMedDate not supplied

Iseluxine: a novel isoquinolinone alkaloid from Iseia luxurians.

A novel isoquinolinone alkaloid, iseluxine (1), has been isolated from the epigeal parts of Iseia luxurians (MORIC.) O'DONELL (Convolvulaceae), a climber indigenous to the tropical Americas. Structural elucidation was achieved by HRMS, 1H NMR, 13C NMR, and HMBC spectroscopy. N- and/or O-methyl derivatives of 1 are already known from certain Magnoliidae families, e.g., the Fumariaceae, the Lauraceae, or the Papaveraceae. Iseluxine, the "missing link" in the biosynthesis of these methyl derivatives from dopamine, is the first isoquinolinone alkaloid characterized by a catechol substructure.

Alkaloids↗
PubMedDate not supplied

[In-migration and the labor market in Tijuana, Baja California].

This interpretative essay on the status of migrant workers in the Tijuana labor market sets up a theoretical framework and specifies the data sources used, including a survey of 672 families in Tijuana in 1982. To define the sphere of analysis, the author discusses demographic behavior and the evolution of the labor market in Tijuana. Within this context, an examination of the work status of migrants is conducted by comparing it to that of the native population, taking into account the characteristics of their regions of origin and factors related to that work status. It is shown that 1) migrants come from areas which are relatively more developed; 2) their work experience is directly related to the nature of the relative degree of development of their regions of origin; 3) there is no difference between the migrants and the native population with regard to the sectors and positions in which they are inserted; and 4) the type of migration tends to be similar to migration taking place in industrialized countries, rather than that characterizing developing countries.

Americas↗