Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.     

Crown alterations induced by decline: a study of relationships between growth rate and crown morphology in beech (Fagus sylvatica L.)

One of the first symptoms expressed by declining trees is reduced growth in stem diameter and length increment. The possibility of a relationship between length increment and crown thinning in beech (Fagus sylvatica L.) was investigated by developing a computer model to simulate first order branching patterns of the apical 2 m of monopodially branching beech trees, 70–100 years old, for a range of length increment rates. The model was based on values for branching angle, main axis and branch length increment, number of branches produced per year and branch mortality rates for six healthy and declining trees. Shoot growth rates in the apical 2 m of the sample trees ranged from about 5 cm/year (decline class 3) to 43 cm/ year (healthy). Simulations of branching patterns in the apical 2 m of trees growing at different rates indicated that, when growth rate exceeded about 20 cm/year, total first order branch length and area explored were independent of growth rate. When growth rates fell below this value there was a reduction in total area explored and first order branch length due primarily to the formation of fewer branches. More acute branching angles contributed to a reduction in the area explored. Growth rate-related crown thinning could increase the risk of bark necrosis and secondary pathogen infection during dry and/or hot spells.     

Capillary operators

The goal of this work is an examination of capillary exchange models as mathematical operators. The concentration function relations for the Krogh cylinder of a single capillary, basic to many organ models, are studied via the theory of operators on the Lebesgue normed spacesL _p[0,∞], (1<-p<-∞). A discussion is included of theL _p -normsvis-à-vis the coefficient of variation currently used in finding capillary parameters and evaluating parameter searches. The capillary model determines two operators on the space of locally integrable functions: O _K (relating extravascular concentration to intravascular) and K _{a, k} (relating intravascular concentration to input), wherek is the ratio of permeabilitysurface area (PS) to extravascular volume, and α is the ratio of PS to flow. These operators are shown to induce contractive (‖O _K ‖ _p <-1, ‖K _{a, k} ‖ _p <-1), isotone, linear operators onL _p . The uniform convergence relation $$K_{a,k} = \mathop {\lim _{(p)} }\limits_{N \to \infty } \left( {\sum\limits_{n = 0}^N {P_n (a)O_k^n } } \right)$$ (as operators onL _p) is derived, whereP _n (a) is the Poisson probabilitye ^?a a ⁿ /n!. For the important special cases ofp=∞, 1, 2 the norms are found (‖O_k‖=‖K_a,k‖_p=1). Consideration is also given to the norms and operators when the functions involved are limited to a finite interval of time.     

ATP and the processivity of Xenopus laevis DNA polymerase α

We use specific restriction fragments as defined primers for DNA synthesis on single-stranded circular phage fd DNA. These structures are relatively poor templates for a highly purified DNA polymerase α from Xenopus laevis eggs. However, DNA synthesis is stimulated about 5-fold by addition of ATP to the reaction mixture. We show that the deoxynucleotide polymers, synthesized in the presence of ATP, are significantly longer than those produced in the absence of ATP. We also show that this effect is due to a more tenacious binding of DNA polymerase α to DNA and conclude that ATP increases the processivity of the enzyme.     

Vascular reactions to horseradish peroxidase in the guinea pig

Summary Albino guinea pigs were given intradermal injections of the protein tracer horseradish peroxidase. In a 0.1 mM concentration the tracer did not increase vascular permeability to Evans blue-labelled plasma proteins. In a 1 mM concentration, however, the peroxidase induced a local vascular leakage. This leakage was almost totally inhibited by pretreating the animals with acetylsalicylic acid, while antihistamine had only a weak inhibitory effect. We therefore believe that prostaglandins are important mediators in this HRP-induced vascular reaction.     

The xylanase introns from Cryptococcus albidus are accurately spliced in transgenic tobacco plants

The xylanase gene from Cryptococcus albidus contains seven introns. Genomic and cDNA clones under the control of the CaMV 35S promoter were transferred into tobacco plants using Agrobacterium-mediated cell transformation. The genes were transcribed and the mRNAs were amplified by the polymerase chain reaction using primers on each side of the intron region. About 90% of the amplification products from plants transformed with the genomic clone corresponded to the size of the pre-mRNA (1.2 kb) and 10% represented the spliced product (0.85 kb). The 0.85 kb fragment was cloned and sequenced and the result indicated that the introns from the xylanase gene were accurately spliced by the plant cells.     

A substance released by metamorphosing larvae and young polyps ofHydractinia echinata induces metamorphosis in conspecific larvae

Summary A metamorphosis-inducing factor was isolated from medium conditioned by either metamorphosing larvae or 3-day postmetamorphic primary polyps. The factor has a molecular weight 8 kDa and is heatlabile. It does not induce metamorphosis of isolated posterior fragments and is therefore not identical to the internal signal described by Schwoerer-Böhning et al. (1990). The biological significance of the substance is currently unclear, therefore its inducing activity may be a side effect.     

N-bromoacetyl-D-leucylglycine. An affinity label for neutral endopeptidase 24.11

Neutral endopeptidase 24.11 is rapidly inactivated by N-bromoacetyl-D-leucylglycine in a reaction which follows first-order kinetics at pH 8 and 37 degrees C. The concentration dependence of inactivation revealed saturation kinetics with an apparent Ki of 10 mM and kappa inact of 0.4 min-1 at saturating inhibitor concentration. Enzyme can be protected from inactivation by either the substrate Leu5-enkephalin or the competitive inhibitors Phe-Gly or Phe-Ala. Inactivation of enzyme by N-bromo-[14C]acetyl-D-leucylglycine proceeds with the incorporation of a stoichiometric amount of labeled inhibitor. Tryptic digestion of the radioactively labeled enzyme followed by high performance liquid chromatography allowed the isolation of a modified peptide with the sequence T-D-V-H-S-P-G-N-F-R in which histidine (His704) is the modified residue. Site-directed mutagenesis was used to generate a mutant form of the enzyme in which histidine 704 was converted to a glutamine residue. This mutant enzyme retained less than 0.1% of the activity of the native enzyme. These results demonstrate that His704 is at the active site of neutral endopeptidase 24.11 and suggest a catalytic role for this residue.     

Oxygenation of malignant tumors after localized microwave hyperthermia

Summary The oxyhemoglobin saturation (HbO₂) of single red blood cells within tumor microvessels (diameter: 3–12 µm) of DS-Carcinosarcoma was studied using a cryophotometric micromethod. In untreated control tumors (mean tissue temperature approx. 35° C) the measured values scattered over the whole saturation range from zero to 100 sat.%, the mean being 51 sat.%. Upon heating at 40° C for 30 min, the oxygenation of the tumor tissue significantly improved as compared with control conditions. After 40° C-hyperthermia a mean oxyhemoglobin saturation of 66 sat.% was obtained. In contradistinction to this, after 43° C-hyperthermia the tumor oxygenation was significantly lower and reached a mean HbO₂ saturation value of 47 sat.%. A further temperature rise to 45° C caused the oxygenation to drop drastically (mean oxyhemoglobin saturation value: 24 sat.%). This is due to a severe restriction of nutritive blood flow.The changes in tumor oxygenation after hyperthermia seem to be predominantly mediated through changes in tumor blood flow, including tumor microcirculation, which showed a similar temperature dependence. Metabolic effects probably play a minor role in the oxyhemoglobin saturation distribution within tumor microvessels.Supported by the Deutsche Forschungsgemeinschaft (Va 57/2-1). Presented in part at the International Symposium on Biomedical Thermology, June 30 to July 4, 1981, Strasbourg, France