Dierk Martin
Agricultural Research Service
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British Journal of Nutrition | 2000
Eckhard Schlimme; Dierk Martin; Hans Meisel
Nucleotides, nucleosides and nucleobases belong to the non-protein-nitrogen (NPN) fraction of milk. The largest amounts of ribonucleosides and ribonucleotides--ribose forms only were considered in this review--were measured directly after parturition in bovine milk and other ruminants as well as in the milk of humans. Generally, concentrations of most of the nucleos(t)ides tend to decrease gradually with advancing lactation period or nursing time. The species-specific pattern of these minor constituents in milk from different mammals is a remarkable property and confirms, at least, the specific physiological impact of these minor compounds in early life. The physiological capacity of these compounds in milk is given by the total potentially available nucleosides. The main dietary sources of nucleos(t)ides are nucleoproteins and nucleic acids which are converted in the course of intestinal digestion into nucleosides and nucleobases the preferred forms for absorption in the intestine. Thus, nucleosides and nucleobases are suggested to be the acting components of dietary and/or supplemented nucleic acid-related compounds in the gut. They are used by the body as exogenous trophochemical sources and can be important for optimal metabolic functions. Up to 15 % of the total daily need for a breast-fed infant was calculated to come from this dietary source. Concerning their biological role they not only act as metabolites but are also involved as bioactive substances in the regulation of body functions. Dietary nucleotides affect immune modulation, e.g. they enhance antibody responses of infants as shown by a study with more than 300 full-term healthy infants. Dietary nucleos(t)ides are found to contribute to iron absorption in the gut and to influence desaturation and elongation rates in fatty acid synthesis, in particular long-chain polyunsaturated fatty acids in early stages of life. The in vitro modulation of cell proliferation and apoptosis has been described by ribonucleosides, in particular by modified components using human cell culture models. Due to the bio- and trophochemical properties of dietary nucleos(t)ides, the European Commission has allowed the use of supplementation with specific ribonucleotides in the manufacture of infant and follow-on formula. From the technochemical point of view, the ribonucleoside pattern is influenced by thermal treatment of milk. In addition ribonucleosides are useful indicators for quantifying adulterations of milk and milk products.
FEBS Letters | 1998
Hans Meisel; Sonja Günther; Dierk Martin; E. Schlimme
The in vitro modulation of apoptosis and cell proliferation by modified in comparison with non‐modified ribonucleosides was investigated for the first time using peripheral blood lymphocytes, HL‐60 cells and Caco‐2 cells as human cell culture models. Modulating effects of several ribonucleosides were found in the range of 10−7–10−3 mol/l. The following ribonucleosides induced significant apoptosis of HL‐60 cells: adenosine, N 6‐dimethyladenosine, N 6‐(2‐isopentenyl)‐adenosine, N 2‐dimethylguanosine. A significant apoptotic effect on PBL was found with N 6‐dimethyladenosine and N 6‐(2‐isopentenyl‐adenosine. N 6‐Dimethyladenosine, N 6‐(2‐isopentenyl)‐adenosine and guanosine had a pronounced inhibitory effect on Caco‐2 cell apoptosis. Regarding the known function of ribonucleosides as pathobiochemical marker molecules for cancer, the possibility of a selective apoptotic effect against malignant cells is discussed.
Journal of Astm International | 2008
W. Clint Hoffmann; Andrew J. Hewitt; Jb Ross; W. E. Bagley; Dierk Martin; Bradley K. Fritz
Spray droplet size has long been recognized as the most important variable that aerial applicators can influence to mitigate spray drift from the application site. There are several different technologies that are used by researchers to measure droplet size from spray nozzles. The objective of these studies was to determine the influence of eight spray adjuvants on the droplet size spectrum produced by two nozzles in a high-speed wind tunnel when characterized using three different droplet size measurement systems. The adjuvant, nozzles, and airspeeds used in these studies are commonly used by aerial applicators. Three droplet sizing systems (Malvern laser diffraction, PMS optical array probe, and LaVision laser imaging) were simultaneously operated to measure the spray droplet size spectra for each adjuvant, airspeed, and nozzle combination. Two spray nozzles (a D6-46 nozzle and a D2 straight stream nozzle) were evaluated in a high-speed wind tunnel at airspeeds of 45 and 58 m/sec. There were significant differences in the droplet size spectra produced by the eight spray adjuvants tested. There were also significant differences between the droplet size values reported by the three measurement systems (Malvern, LaVision, and PMS) evaluated; however, there was considerable agreement trendwise. In general, the Malvern reported smaller spray droplet size spectra values than the LaVision, while the PMS system generally reported the largest spray droplet size spectra values. These tests are the first reported studies where all three droplet sizing systems were operated simultaneously.
Zeitschrift für Naturforschung C | 1994
Dierk Martin; E. Schlimme
The hypermodified ureidonucleoside N6[((9-β-ᴅ-ribofuranosyl-9H-purine-6-yl)amino)carbonyl]- ʟ-threonine (5) is a constituent of transfer ribonucleic acid (tRNA) and is secreted as a tRNA catabolite in body fluids such as blood, milk and urine. Compound 5 and the isomeric ureidonucleosides bearing ᴅ-threonine (9), ʟ-allo- (7) and ᴅ-allo-threonine (11) as side chain moieties were synthesized on a preparative scale. The amido protons of 5 and 9 cause two separate 1H NMR signals whereas 7 and 11 cause multiplets. The 13C NMR signals of all carbon atoms of the allo-amino acid side chains (7, 11) are shifted downfield of the corresponding signals in compounds 5 and 9. The chemically protected intermediate compound adenosine urethane (3) is potentially of interest in the analysis of amino acids because it may be converted to nucleosides of the ureido type by reaction with amino acids in biological matrices.
In: Encyclopedia of Dairy Sciences. Academic Press, San Diego, pp. 971-979. | 2011
Dierk Martin; E. Schlimme; David Tait
Nucleosides are N-glycosides of pyrimidines and purines; nucleotides are o-phosphoric esters thereof. Both groups of compounds belong to the bioactive substances in milk and colostrum. They are part of the nonprotein-nitrogen fraction of milk. The concentration pattern is specific for the milk of a given species. The physiological capacity of these compounds in milk is given by the total potentially available nucleosides, that is, all potential sources available in milk for the generation of these compounds by digestion and metabolism. Owing to their biofunctional properties, nucleotides are used as supplements in infant formulae. The relatively constant concentration pattern of nucleosides throughout lactation changes markedly on milk processing. Thus, nucleosides are useful indicators in dairy technology, for example, for distinguishing butter types as well as for the characterization of heat and high-pressure treatment. In addition, the species-specific patterns of nucleoside contents are particularly recognizable in the unmodified nucleoside contents and by calculation of the concentration ratios of unmodified and modified nucleosides. Thus, nucleoside determination is suitable for distinguishing raw milk from cow, sheep, and goat.
Current Pharmaceutical Design | 2007
Dierk Martin; Hans Meisel
Naturally occurring and chemically modified ribonucleosides have interesting bioactive effects. Dietary ribonucleosides are ingested mainly as nucleoproteins and are converted in the course of intestinal digestion to monomeric compounds. Different bioactive effects of dietary ribonucleosides have been described, including the ability to enhance gut growth and maturation and to increase iron absorption. Cytochemical studies with human cells showed that several ribonucleosides can induce apoptosis in human cells, and therefore may be potentially anticancerogenic compounds. Even if suboptimal concentrations of single bioactive nucleo compounds are available from food, the total content of different bioactive ribonucleosides may reach physiologically effective concentrations in vivo where intestinal cells may represent the main target sites of a selective apoptotic activity. Modified ribonucleosides serve as valuable pathobiochemical marker molecules for cancer. Chemically modified ribonucleosides have already found interesting applications as pharmaceutically active compounds in the treatment of different illnesses including AIDS. Regarding therapeutic and pharmaceutical aspects, further studies are required to evaluate the bioactive efficacy of indigenous ribonucleosides. The findings demonstrate the great variety of potential applications of ribonucleosides, e.g. in functional foods as well as pharmaceutical preparations.
International Journal of Dairy Technology | 2006
Wolfgang Hoffmann; Christian Kiesner; Ingrid Clawin-Rädecker; Dierk Martin; K. Einhoff; Peter Christian Lorenzen; Hans Meisel; Philipp Hammer; Gertraud Suhren; P. Teufel
International Journal of Dairy Technology | 2011
Peter Chr. Lorenzen; Ingrid Clawin-Rädecker; K. Einhoff; Philipp Hammer; Rainer Hartmann; Wolfgang Hoffmann; Dierk Martin; Joachim Molkentin; Hans G Walte; Michael Devrese
Small Ruminant Research | 2010
P. Chr. Lorenzen; Dierk Martin; Ingrid Clawin-Rädecker; K. Barth; K. Knappstein
Kieler Milchwirtschaftliche Forschungsberichte | 2000
R. Hartmann; S. Günther; Dierk Martin; Hans Meisel; A. K. Pentzien; E. Schlimme; N. Scholz