Showing papers by "University of Hohenheim published in 1992"
TL;DR: Two bacteriocin producing strains,one of Lactobacillus curvatus and one of L. sake, have been isolated employing a catalase-containing bacteriOCin-screening-medium for lactobacilli, and were not only active against closely related lactOBacilli but also against the opportunistic food pathogens Listeria monocytogenes and Enterococcus faecalis.
264 citations
TL;DR: In this article, the estrogen-sensitive cell lines (MCF-7 cells and LeC-9 cells) were used to determine the estrogenic activities of purified compounds of vegetable origin (myco- and phytoestrogens) and zearalenone-contaminated forage cereals (wheat, barley and oats).
182 citations
TL;DR: For in vivo demonstration of acid phosphatase activity in the rhizosphere of soil-grown plants filter papers were treated with a mixture of 1-naphthyl phosphate as substrate and the diazonium salt Fast Red TR as an indicator.
Abstract: For in vivo demonstration of acid phosphatase activity in the rhizosphere of soil-grown plants filter papers were treated with a mixture of 1-naphthyl phosphate as substrate and the diazonium salt Fast Red TR as an indicator. After enzymatic hydrolysis, 1-naphthol forms a red complex with Fast Red TR. This method was applied to 8-day old maize plants and 3-year old Norway spruce plants growing in rhizoboxes in soil under non-sterile conditions. The treated filter paper is placed at the surface of roots and soil and acid phosphatase activity is visualized as a red-coloured ‘root print’ on the filter paper. The method can be used as a qualitative analysis of acid phosphatase in the rhizosphere. It also allows a rough estimate of phosphatase activity in different root zones.
171 citations
TL;DR: In this paper, the root-induced oxidation processes in the rhizosphere depended on the atmospheric oxygen supply to the roots, and the radius of the redox RHizosphere varied from less than 1 mm in strongly reduced soil up to 4 mm in a weakly reduced one.
Abstract: Redox potentials in microsites of the rhizosphere of flooded rice were continuously measured for several days. Close to the root tips redox potential markedly increased. The highest increase was measured in the rhizosphere of the tips of short lateral roots. Aerobic redox conditions were reached there, except in a very strongly reduced soil. Both the extension of the oxidation zone around the root tips and the maximum redox potential reached were influenced by the reducing capacity of the soil. The radius of the redox rhizosphere varied from less than 1 mm in a strongly reduced soil up to 4 mm in a weakly reduced one. The root-induced oxidation processes in the rhizosphere depended on the atmospheric oxygen supply to the roots.
145 citations
TL;DR: In this article, the in-vitro degradability of protein and neutral-detergent fiber (NDF) was determined in 72 West African fodder trees and shrubs.
Abstract: Relationships among soluble phenolics, soluble and insoluble proanthocyanidins (PAC), lignin, N, neutral-detergent fibre (NDF), and in-vitro degradability of protein and NDF were determined in 72 West African fodder trees and shrubs. Species were collected in the semi-arid (Niger), sub-humid (Nigeria) and humid/sub-humid (Benin) zones. Variation among species in chemical composition and in-vitro degradability of protein and NDF was large. Zones did not differ in mean content of phenolic compounds. Protein degradability was negatively correlated with soluble phenolics (r = −0.34, P < 0.01) and soluble PAC (r = −0.47, P < 0.001). NDF was positively correlated with soluble PAC (r = 0.44, P < 0.001), insoluble PAC (r = 0.28, P < 0.05) and lignin (r = 0.76, P < 0.001). NDF degradability was negatively correlated with soluble PAC (r = −0.40, P < 0.001) and lignin (r = −0.59, P < 0.001). Chemical composition and in-vitro degradability along with field observations can provide useful criteria for determining the nutritive value of browse species.
135 citations
TL;DR: In this paper, restriction fragment length polymorphisms (RFLPs) have been proposed for the prediction of the yield potential of hybrids and the assignment of inbreds to heterotic groups.
Abstract: Restriction fragment length polymorphisms (RFLPs) have been proposed for the prediction of the yield potential of hybrids and the assignment of inbreds to heterotic groups. Such use was investigated in 66 diallel crosses among 6 flint and 6 dent inbreds from European maize (Zea mays L.) germ plasm. Inbreds and hybrids were evaluated for seven forage traits in four environments in the Federal Republic of Germany. Midparent heterosis (MPH) and specific combining ability (SCA) were calculated. Genetic distances (GD) between lines were calculated from RFLP data of 194 clone-enzyme combinations. GDs were greater for flint x dent than for flint x flint and dent x dent line combinations. Cluster analysis based on GDs showed separate groupings of flint and dent lines and agreed with pedigree information, except for 1 inbred. GDs of all line combinations in the diallel were partitioned into general (GGD) and specific (SGD) genetic distances; GGD explained approximately 20% of the variation among GD values. For the 62 diallel crosses (excluding 4 crosses of highly related lines), correlations of GD with F1 performance, MPH, and SCA for dry matter yield (DMY) of stover, ear, and forage were positive but mostly of moderate size (0.09≤r≤0.60) compared with the higher correlations (0.39≤r≤0.77) of SGD with these traits. When separate calculations were performed for various subsets, correlations of GD and SGD with DMY traits were generally small (r<0.47) for the 36 flint x dent crosses, significantly positive (r<0.53) for the 14 flint x flint crosses, and inconclusive for the 12 dent x dent crosses because of the lack of significant genotypic variation. Results indicated that RFLPs can be used for assigning inbreds to heterotic groups. RFLP-based genetic distance measures seem to be useful for predicting forage yield of (1) crosses between lines from the same germ plasm group or (2) crosses including line combinations from the same as well as different heterotic groups. However, they are not indicative of the hybrid forage yield of crosses between unrelated lines from genetically divergent heterotic groups.
114 citations
TL;DR: The two components of the inducible 2-halobenzoate 1,2-dioxygenase from Pseudomonas cepacia 2CBS were purified to homogeneity and exhibited a very broad substrate specificity, but benzoate analogs with electron-withdrawing substituents at the ortho position were transformed preferentially.
Abstract: The two components of the inducible 2-halobenzoate 1,2-dioxygenase from Pseudomonas cepacia 2CBS were purified to homogeneity. Yellow component B is a monomer (Mr, 37,500) with NADH-acceptor reductase activity. Ferricyanide, 2,6-dichlorophenol indophenol, and cytochrome c acted as electron acceptors. Component B was identified as an iron-sulfur flavoprotein containing 0.8 mol of flavin adenine dinucleotide, 1.7 mol of iron, and 1.7 mol of acid-labile sulfide per mol of enzyme. The isoelectric point was estimated to be pH 4.2. Component B was reduced by the addition of NADH. Red-brown component A (Mr, 200,000 to 220,000) is an iron-sulfur protein containing 5.8 mol of iron and 6.0 mol of acid-labile sulfide. The isoelectric point was within the range of pH 4.5 to 5.3. Component A could be reduced by dithionite or by NADH plus catalytic amounts of component B. Component A consisted of nonidentical subunits alpha (Mr, 52,000) and beta (Mr, 20,000). It contained approximately equimolar amounts of alpha and beta, and cross-linking studies suggested an alpha 3 beta 3 subunit structure of component A. The NADH- and Fe(2+)-dependent enzyme system was named 2-halobenzoate 1,2-dioxygenase, because it catalyzes the conversion of 2-fluoro-, 2-bromo-, 2-chloro-, and 2-iodobenzoate to catechol. 2-Halobenzoate 1,2-dioxygenase exhibited a very broad substrate specificity, but benzoate analogs with electron-withdrawing substituents at the ortho position were transformed preferentially.
109 citations
TL;DR: A gene bank containing MboI fragments of chromosomal DNA from Lactobacillus sake LTH677 in Escherichia coli plasmid pBR328 was constructed and protein analysis revealed that the catalase subunit has a molecular size of 65,000 Da and that the activeCatalase possesses a hexameric structure.
Abstract: Lactobacillus sake LTH677 is a strain, isolated from fermented sausage, which forms a heme-dependent catalase. This rare property is highly desirable in sausage fermentation, as it prevents rancidity and discoloration caused by hydrogen peroxide. A gene bank containing MboI fragments of chromosomal DNA from Lactobacillus sake LTH677 in Escherichia coli plasmid pBR328 was constructed. The catalase gene was cloned by heterologous complementation of the Kat- phenotype of E. coli UM2. The catalase structural gene, designated katA, was assigned to a 2.3-kb region by deletion analysis of the originally cloned fragment in plasmid pHK1000. The original chromosomal arrangement was determined by Southern hybridization. Protein analysis revealed that the catalase subunit has a molecular size of 65,000 Da and that the active catalase possesses a hexameric structure. The molecular size of the subunit deduced from the nucleotide sequence was determined to 54,504 Da. The N-terminal amino acid sequence of the 65,000-Da protein corresponded to the one deduced from the DNA sequence. After recloning of katA in the E. coli-Lactococcus shuttle vector pGKV210, the gene was successfully transferred and phenotypically expressed in Lactobacillus casei, which is naturally deficient in catalase activity.
105 citations
01 Jan 1992
TL;DR: This chapter deals with some aspects of structural barriers impermeable to attempted invasions of pathogens as opposed to more direct pathogen controls by way of phytoalexin antibiotics, hydrolases or fungitoxic thionins.
Abstract: This chapter deals with some aspects of structural barriers impermeable to attempted invasions of pathogens as opposed to more direct pathogen controls by way of phytoalexin antibiotics, hydrolases or fungitoxic thionins. There is growing evidence that such barriers are reinforced or even newly erected in plant defense responses, and that they contribute to disease resistance (Aist, 1983; Hargreaves and Keon, 1986; Delmer and Stone, 1988). Major structural barriers are the cellulosic cell walls, in particular epidermal cell walls, impregnated with lignin polymers and other wallbound phenolics and the cuticle with cutin and soluble waxes as major constituents (Vance et al., 1980; Kolattukudy, 1980, 1985; Kolattukudy and Soliday, 1985).
93 citations
TL;DR: Analyzing the composition of gangliosides in cortical regions during aging, they were observed to follow region-specific alterations, characterized by lowest GD1a in visual cortex.
92 citations
TL;DR: The observations call into question the concept of enteric command neurons in favor of a divergent vagal input with widespread modulatory influences over gastric enteric neurotransmission.
Abstract: Myenteric "command neurons" are thought to be the interface between extrinsic and intrinsic controls of gut functions and are thought to be responsible for transmission of vagal impulses to enteric microcircuits. To identify, electrophysiologically, myenteric neurons responding to electrical stimulation of the vagus, we developed an in vitro preparation of the gastric myenteric plexus in which the vagal innervation was preserved. The majority of myenteric neurons [102 of 155 (66%)] received fast excitatory postsynaptic potentials (fEPSPs) after stimulation of the vagus. The proportion of neurons receiving vagal input was highest at the lesser curve (98%) and decreased gradually when recordings were made from neurons located toward the greater curve. Only a small proportion of neurons (4 of 85 cells) showed a slow EPSP after a burst of vagal stimulation. No postsynaptic inhibitory potentials were observed. There was no preferential vagal input to either gastric I, gastric II, or gastric III neurons. The fEPSPs were due to the release of acetylcholine acting postsynaptically on nicotinic receptors. The behavior of the fEPSPs suggests multiple vagal inputs to a majority of myenteric neurons. Our observations call into question the concept of enteric command neurons in favor of a divergent vagal input with widespread modulatory influences over gastric enteric neurotransmission.
TL;DR: The ability of root-associated microorganisms to affect Fe-uptake rates from siderophore and phytosiderophores, even in short-term uptake experiments, indicates that microorganisms can be an unpredictable confounding factor in experiments examining mechanisms for utilization of microbial siderophile or phytOSiderophorous under nonsterile conditions.
Abstract: Collaborative experiments were conducted to determine whether microbial populations associated with plant roots may artifactually affect the rates of Fe uptake and translocation from microbial siderophores and phytosiderophores. Results showed nonaxenic maize to have 2 to 34-fold higher Fe-uptake rates than axenically grown plants when supplied with 1 μM Fe as either the microbial siderophore, ferrioxamine B (FOB), or the barley phytosiderophore, epi-hydroxymugineic acid (HMA). In experiments with nonsterile plants, inoculation of maize or oat seedlings with soil microorganisms and amendment of the hydroponic nutrient solutions with sucrose resulted in an 8-fold increase in FOB-mediated Fe-uptake rates by Fe-stressed maize and a 150-fold increase in FOB iron uptake rates by Fe-stressed oat, but had no effect on iron uptake by Fe-sufficient plants. Conversely, Fe-stressed maize and oat plants supplied with HMA showed decreased uptake and translocation in response to microbial inoculation and sucrose amendment. The ability of root-associated microorganisms to affect Fe-uptake rates from siderophores and phytosiderophores, even in short-term uptake experiments, indicates that microorganisms can be an unpredictable confounding factor in experiments examining mechanisms for utilization of microbial siderophores or phytosiderophores under nonsterile conditions.
TL;DR: Sorghum flour was fermented in the traditional way for Kisra production using wet or dry preparations of fermented sorghum dough from Sudanese households as inocula, finding that the relative content of most amino acids in the doughs did not significantly change during the fermentation.
Abstract: Sorghum flour was fermented in the traditional way for Kisra production. Wet or dry preparations of fermented sorghum dough from Sudanese households were employed as inocula. Microbiological and chemical analysis was performed throughout the fermentation process. Cell counts reached values of up to 9 × 108 cfu/g and contained >99% lactobacilli. Strains of Lactobacillus fermentum, L. reuteri and L. amylovorus or L. fermentum and L. amylovorus were found as dominant organisms in doughs inoculated with wet or dry sorghum dough preparations, respectively. The ratios of the lactobacilli remained constant after up to four consecutive fermentations. After inoculation with the dry dough preparation the yeast Candida krusei was detected at 106 cfu/g. During the fermentation the pH declined from 5.5 to values of approximately 3.4. The maltose content of the dough decreased continuously, wheraas glucose was accumulated as an intermediate. The relative content of most amino acids in the doughs did not significantly change during the fermentation. However, the concentrations of cysteine and methionine decreased, whereas threonine was enriched in the dough.
TL;DR: RFLP data revealed a wide range of genetic diversity within the two heterotic groups assayed, Iowa Stiff Stalk Synthetic (BSSS) and Lancaster Sure Crop (LSC), and principal coordinate and cluster analyses based on GS values resulted in the separate groupings of lines, which is consistent with known pedigree information.
Abstract: The objectives of this study were (1) to investigate genetic diversity for RFLPs in a set of important maize inbreds commonly used in Italian breeding programs, (2) to compare genetic similarities between unrelated lines from the same and different heterotic groups, and (3) to examine the potential of RFLPs for assigning maize inbreds to heterotic groups. Forty inbreds were analyzed for RFLPs with two restriction enzymes (EcoRI and HindIII) and 82 DNA clones uniformly distributed over the maize genome. Seventy clone-enzyme combinations gave single-banded RFLP patterns, and 79 gave multiple-banded RFLP patterns. The average number of RFLP patterns detected per clone-enzyme combination across all inbreds was 5.8. RFLP data revealed a wide range of genetic diversity within the two heterotic groups assayed, Iowa Stiff Stalk Synthetic (BSSS) and Lancaster Sure Crop (LSC). Genetic similarity (GS) between lines was estimated from binary RFLP data according to the method of Nei and Li (1979). The mean GS for line combinations of type BSSS × LSC (0.498) was substantially smaller than for unrelated line combinations or type BSSS × BSSS (0.584) but almost as great as for un-related line combinations of type LSC × LSC (0.506). Principal coordinate and cluster analyses based on GS values resulted in the separate groupings of lines, which is consistent with known pedigree information. A comparison between both methods for multivariate analyses of RFLP data is presented.
TL;DR: Results from this study corroborated that RFLP data can be used for assigning inbreds to heterotic groups and revealing pedigree relationships among in breds.
Abstract: Thirty inbred lines representing a wide range of early-maturing European elite germ plasm of maize (Zea mays L.) were assayed for RFLPs using 203 clone-enzyme combinations (106 DNA clones with restriction enzymes EcoR1 and HindIII). The genetic materials comprised 14 flint, 12 dent, and 4 lines of miscellaneous origin. Objectives were to (1) characterize the genetic diversity for RFLPs in these materials, (2) compare the level of genetic diversity found within and between the flint and the dent heterotic groups, and (3) examine the usefulness of RFLPs for assigning inbreds to heterotic groups. All but two DNA clones yielded polymorphism with at least one restriction enzyme. A total of 82 and 121 clone-enzyme combinations gave single-banded and multiple-banded RFLP patterns, respectively, with an average of 3.9 and 7.7 RFLP patterns per clone-enzyme combination across all 30 inbreds, respectively. Genetic similarity (GS) between lines, estimated from RFLP data as Dice's similarity coefficient, showed considerable variation (0.32 to 0.58) among unrelated inbreds. The mean GS for line combinations of type flint x dent (0.41) was significantly smaller than for unrelated flint lines (0.46) and dent lines (0.46), but there was considerable variation in GS estimates of individual line combinations within each group. Cluster and principal coordinate analyses based on GS values resulted in separate groupings of flint and dent lines in accordance with phylogenetic information. Positioning of lines of miscellaneous origin was generally consistent with expectations based on known breeding behavior and pedigrees. Results from this study corroborated that RFLP data can be used for assigning inbreds to heterotic groups and revealing pedigree relationships among inbreds.
TL;DR: DNA sequence analysis revealed an open reading frame encoding a predicted polypeptide with the same M(r) and N-terminal amino acid sequence as the purified subunit of BPO-A2, which showed the same electrophoretic and immunological properties as the bromoperoxidase BPO -A2 purified from S. aureofaciens ATCC 10762.
Abstract: A bromoperoxidase gene (bpoT), recently cloned from Streptomyces aureofaciens Tu24, was used as a probe in Southern blot hybridization of total DNA from S. aureofaciens ATCC 10762. A single SstI fragment of 5·4 kb was detected, which was cloned via an enriched gene library into Escherichia coli. The functional bromoperoxidase gene was located on a 2.1 kb BamHI-HindIII fragment by subcloning into S. lividans TK64, using the multicopy plasmid pIJ486. The enzyme was overproduced in S. lividans TK64 (up to 30000 times compared to S. aureofaciens ATCC 10762) and showed the same electrophoretic and immunological properties as the bromoperoxidase BPO-A2 purified from S. aureofaciens ATCC 10762. DNA sequence analysis revealed an open reading frame encoding a predicted polypeptide with the same M
r and N-terminal amino acid sequence as the purified subunit of BPO-A2.
TL;DR: To the authors' knowledge this is the first report of PGF 2 α and estrogen concentrations in the stallion ejaculate, and a tendency was found for higher mean estrone sulphate concentrations than for total free steroid in both seminal and blood.
TL;DR: In this article, the nucleophilic replacement of one halogen atom (chlorine, fluorine) in the trihalo-s-triazines (2,4,6-trihalo 1,3,5-triazine) by reaction with selected d - or l -amino acids to form diastereomeric derivatives which were separated by reverse-phase (C18) high-performance liquid chromatography by using mixtures of water, acetonitrile and trifluoroacetic acid as eluents.
TL;DR: Glasshouse trials were performed to investigate the control of the parasitic weed Striga hermonthica by Fusarium nygamai and the performance of the host plant sorghum using different inoculum substrates and inoculum amounts of the fungus.
TL;DR: The chromatographic methods discussed in this review allow the rapid, sensitive and non-ambiguous determination of individual species of the two most important phycotoxins in seafood, PSP and DSP.
TL;DR: In this article, it has been demonstrated that fibroblast cell systems of Valo-chicken, C3H-mice, BN-rats, and man are stem cell systems.
01 Jan 1992
TL;DR: In this paper, the effect of fertilizer and micronutrient (MN) application on groundnut growth and symbiotic N2-fixation of groundnut (Arachis hypogaea L).
Abstract: Two field experiments were conducted in 1988 and 1989 on an acid sandy soil in Niger, West Africa, to assess the effect of phosphorus (P), nitrogen (N) and micronutrient (MN) application on growth and symbiotic N2-fixation of groundnut (Arachis hypogaea L.). Phosphorus fertilizer (16 kg P ha−1) did not affect pod yields. Addition of MN fertilizer (100 kg ‘Fetrilon Combi 1’ ha−1; P + MN) containing 0.1% molybdenum (Mo) increased pod yield by 37–86%. Nitrogen concentration in shoots at mid pod filling (72 days after planting) were higher in P + MN than in P − MN fertilizer treatment. Total N uptake increased from 53 (only P) to 108 kg N ha−1 by additional MN application. Seed pelleting (P + MoSP) with 100 g Mo ha−1 (MoO3) increased nitrogenase activity (NA) by a factor of 2–4 compared to P treatment only. The increase in NA was mainly due to increase in nodule dry weight and to a lesser extent to increase in specific nitrogenase activity (SNA) per unit nodule dry weight. The higher NA of the P + MoSP treatment was associated with a higher total N uptake (55%) and pod yield (24%). Compared to P + MoSP or P + MN treatments application of N by mineral fertilizer (60 kg N ha−1) or farmyard manure (130 kg N ha−1) increased only yield of shoot dry matter but not pod dry matter. Plants supplied with N decreased soil water content more and were less drought tolerant than plants supplied with Mo. The data suggest that on the acid sandy soils in Niger N deficiency was a major constraint for groundnut production, and Mo availability in soils was insufficient to meet the Mo requirement for symbiotic N2-fixation of groundnut.
TL;DR: In this paper, the authors characterized the shoot demand for nutrients per unit root at sub-optimal RZT and compared the root-to-shoot translocation rates of N, P, K, and Ca from the roots to the shoot to shoot demand.
Abstract: Root growth and nutrient uptake rates of maize (Zea mays L.) are decreased at low root zone temperatures (RZT) and thus, shoot growth may be limited by nutrient deficiency. The objectives of this research were to characterize the shoot demand for nutrients per unit root at suboptimal RZT and to relate net translocation rates of N, P, K, and Ca from the roots to the shoot to shoot demand. Maize plants were grown for 11 days in soil or 8 days in nutrient solution at uniform shoot (24°/20°C, day/night) but different RZT (12°, 18°, and 24°C). The shoot base of the plants (apical shoot meristem and zone of leaf extension) was either kept within or above the cooled root zone.
Shoot and root growth were significantly reduced at suboptimal RZT (12°, 18°). Lifting the shoot base above the cooling zone increased shoot growth markedly, whereas root growth was not significantly influenced. Thus, the shoot fresh weight increment day−1 g−1 root fresh weight (i.e. the shoot demand per unit root) was increased by a factor of up to 9 for plants with their shoot base above as compared to within the cooling zone.
At suboptimal RZT, translocation rates of N, K, and Ca to the shoot remained low in plants with the shoot base in the cooling zone but were higher than in 24°C-grown plants, when the shoot base was above the cooling zone. In both nutrient solution- and soil-grown plants translocation rates of N, K, and Ca were closely correlated with the shoot demand per unit root but less to RZT. In contrast, the translocation rate of P was mainly affected by RZT but insensitive to shoot demand and, therefore, was always higher at a RZT of 24° than of 12°C.
From these results it is suggested, that at low RZT the root-to-shoot translocation rates of N, K, and Ca are mainly determined by the shoot demand, whereas the translocation rate of P, regardless of the shoot demand, is reduced by a direct effect of low temperature on the roots.
TL;DR: In this paper, the most abundant toxaphene congeners in marine mammals and fish were isolated from 3.5 kg seal blubber using reverse phase high performance liquid chromatography (HPLC).
TL;DR: The abaxial and adaxial leaf surfaces oficuticular leaf waxes of Ginkgo biloba, Magnolia grandiflora and Liriodendron tulipifera show most different micromorphological wax ultrastructures, as shown for all trees studied.
Abstract: Epicuticular leaf waxes of Ginkgo biloba, Magnolia grandiflora and Liriodendron tulipifera contain homologous series of hydrocarbons, wax esters, benzyl acyl esters, aldehydes, primary alcohols, and fatty acids. None of these lipid classes is found to contain any main component dominating. In addition to these usual wax lipids, in G. biloba leaf wax a secondary alcohol namely nonacosan-10-ol (15.0%), γ-tocopherol (1.7%) and acetates (0.3%) is also present. The wax of L. tulipifera, however, contains hentriacontan-16-one (23%) and several triterpenols (10%), additionally. On G. biloba leaves a dense arrangement of tubular wax crystalloids are found on the lower as well as on the upper leaf surface. The openings of the tubules can be seen very well in the SEM figures at a magnification of 20000. The small tubules are a clear indication for the presence of nonacosan-10-ol as also reported previously for conyferyl waxes. Leaves of M . grandiflora have an abaxial epidermis with a continuous wax layer without any crystalloids or sculptures. The adaxial epidermis also shows a continuous wax layer but with little irregular granular sculptures. L. tulipifera leaves show an abaxial epidermis with a continuous wax layer superimposed by a dense arrangement of crystalloids in shape of angular rodlets which are composed of several piled up layers. The adaxial leaf surface is also superimposed with wax crystalloids, the rodlets of which, however, are not sculptured in such definite way. They usually appear melted up and also form granular sculptures. The wax crystalloids in shape of angular rodlets on the abaxial surface are formed by hentriacontan-16-one. The abaxial and adaxial leaf surfaces show most different micromorphological wax ultrastructures, as shown for all trees studied.
TL;DR: Four zones are distinguished within the Central Namib fog desert lichen field, each dominated by a growth form indicating various influences of different climatic, geomorphic or biogenic parameters.
Abstract: Number, geographic location, extent and characteristics of lichen fields were recorded within the Central Namib fog desert. Their occurrence is restricted to stable surfaces in the near coastal belt, while percentage cover changes with exposure, elevation and distance from the coastline. Maximum coverage of 70% was found at a distance of 5 km from the coast near Wlotzkas Baken. The highest biomass rate of 400 mg/m2 was measured here at a distance of 1 km from the coast, where Teloschistes capensis appears as cushion growth type. Distribution patterns on hills, riverbeds and polygon structures are described. In general, fruticose and foliose lichens dominate on SW-exposed, ocean-facing habitats. Crustose species dominate on NE-E-exposed plots.
TL;DR: Investigation into the molecular mechanisms of the cellular aging of secondary fibroblast populations in vitru found that secondary human embryonic lung fibroblasts undergo a finite number of 50 ?
Abstract: The life span of higher eukaryotic organisms such as vertebrates, mammals, and primates can be divided into five phases of development: embryonic, juvenile, adolescent, senescent, and the phase of death. It is very likely that the five stages of development are under the control of genetic programs. The molecular mechanisms of aging can be studied on several levels of biological complexity: the organism, the organ, the tissue, and the cell system. Investigations of the molecular mechanisms of cellular aging of cells in cell systems represent research at the lowest state of biological complexity. The human organism is made up of about 400 cell systems,' the majority of which are cell systems with specialized functions such as the keratinoblastkeratinocyte cell system. In addition, there are two cell systems with helper or accessory functions, the glia cell systems of the brain and the fibroblast cell systems of the connective tissues. Evidence is accumulating that makes it likely that all cell systems are stem cell systems with a design resembling that of the hematopoietic stem cell systems.*J Numerous investigations into the molecular mechanisms of the cellular aging of secondary fibroblast populations in vitru have been undertaken in the last three decades, after Hayflick and Moorhead4 described that secondary human embryonic lung fibroblasts undergo a finite number of 50 ? 10 cumulative population doublings and then die. The culture history of these cells was divided into three phases, phase I representing the establishment of the population in vitru, phase I1 the period of serial transfer and exponential increase in cell number, and phase 111 the exhaustion of the proliferative capacity, the phase 111 phenomenon, which was interpreted to be aging at the celluler level. The nondividing cells degenerated spontaneously after varying periods of time in stationary c ~ l t u r e . ~ Distinct morphotypes and quantitative and/or qualitative disparities for a multitude of biochemical parameters are recorded for these secondary human fibroblasts in early and late passage in vitro. No attempts have been made to correlatc the distinct fibroblast cell types with dissimilarities in biochemical parameters in secondary fibroblasts at nonidentical passage levels. The nature of the fibroblast cell system was not cleared up. As a result, biological and biochemical studies were undertaken with undefined secondary fibroblast populations, and many data described contra-
TL;DR: It is concluded that intake of free D-AA found in food is no threat for human beings because of the presence of D-amino acid oxidases in human kidney, liver, and brain.
Abstract: Free L- and D-amino acids (L-AA, D-AA) were isolated from an Appenzeller cheese, from raw milk, and from an ethanolic extract as well as a total hydrolysate of cow's rumen microorganisms, and their relative amounts were determined by reversed-phase high-performance liquid chromatography after derivatization witho-phthaldialdehyde together withN-isobutyryl-L-(or D)-cysteine. D-Ala, D-Asp and D-Glu were found, among other D-AA in all cases and a microbial origin of free D-AA found in cheese and milk was rationalized. From the results, and taking other findings of the occurrence of D-AA in food and beverages into account, the highest intake of D-AA is to be expected from the consumption of ripened cheeses. From the presence of D-amino acid oxidases in human kidney, liver, and brain and from reports on the intravenous administration of racemic AA to humans and their metabolisation it is concluded that intake of free D-AA found in food is no threat for human beings.