FITC-labeled lectins and calcofluor white ST as probes for the investigation of the molecular architecture of cell surfaces. Studies on conjugatophycean species

Summary In a screening program with 7 FITC-labeled lectins as probes, ConA receptors were identified in all of the 28 members of theConjugatophyceae, being under investigation. In nearly all of them RCA₁₂₀ receptors, too, are expressed. In 3 species only, PNA receptors, and in 2 species UEA receptors have been detected. No binding of DBA, SBA, and WGA was observed. The receptors for ConA, RCA₁₂₀, and UEA were shown to be associated with different molecules. Each lectin exhibits a unique and specific binding pattern, both chemically, as well as with regard to the topographic distribution on cell surfaces. While ConA receptors predominantly are associated with constituents of the cell wall, RCA₁₂₀ receptors mostly form part of the surrounding mucilage; the same holds for UEA receptors. Besides a variability of topographic distribution and species-to-species variation, a cell-to-cell variation exists in many species, suggesting that the expression of a lectin receptor is due to the developmental state of the cell and/or depends on external stimuli. In conclusion, we may point out, that FITC-labeled lectins turned out to be extremely useful probes for the investigation of the molecular architecture of cell walls. Calcofluor white ST binding to fibrillar polysaccharides (most probably cellulose) was shown to be inhibited by external incrustations of the cell wall. One species does not show any reaction with calcofluor white ST at all.     

Biochemical Changes that Occur during Senescence of Wheat Leaves : I. Basis for the Reduction of Photosynthesis

Changes in activities of photosynthetic enzymes and photochemical processes were followed with aging of vegetative and flag leaves of wheat (Triticum aestivum L. cv Roy). Activities of stromal enzymes began to decline prior to photochemical activities. In general, total soluble protein and the activities of ribulose-1,5-bisphosphate carboxylase and NADP-triose-phosphate dehydrogenase declined in parallel and at an earlier age than leaf chlorophyll (Chl), leaf photosynthesis, and photosynthetic electron transport activity. Leaves appeared to lose whole chloroplasts as opposed to a general degradation of all chloroplasts based on three lines of evidence: (a) electron transport activity calculated on an area basis declined much earlier than the same data expressed on a Chl basis; (b) Chl content per chloroplast was similar for mature and senescent tissue; and (c) the absorbance at 550 nanometers (light scattering) per unit of Chl remained essentially constant until the end of senescence. Chloroplasts did, however, undergo some modifications before they were lost (e.g. loss of stromal enzyme activities), but the reduction in leaf photosynthesis was apparently caused by a loss of whole chloroplasts.     

Quantitation of gibberellins and the metabolism of [3H]gibberellin A1 during somatic embryogenesis in carrot and anise cell cultures

In a carrot (Daucus carota L.) cell line lacking the ability to undergo somatic embryogenasis, and in carrot and anise (Pimpinella anisum L.) cell lines in which embryogenesis could be regulated by presence or absence of 2,4-dichlorophen-oxyacetic acid (2,4-D), in the medium (+2,4-D=no embryogenesis,-2,4-D=embryo differentiation and development), the levels of endogenous gibberellin(s) (GA) were determined by the dwarfrice bioassay, and the metabolism of [³H]GA₁ was followed. Embryos harvested after 14 d of subculture in-2,4-D had low levels (0.2–0.3 g g^-1 dry weight) of polar GA (e.g. GA₁-like), but much (3–22 times) higher levels of less-polar GA (GA_4/7-like); GA₁, GA₄ and GA₇ are native to these cultures. Conversely, the undifferentiated cells in a non-embryogenic strain, and proembryos of an embryogenic strain (+2,4-D) showed very high levels of polar GA (2.9–4.4 g g^-1), and somewhat reduced levels of less-polar GA. Cultures of anise undergoing somatic embryo development (-2,4-D) metabolized [³H]GA₁ very quickly, whereas proembryo cultures of anise (+2,4-D) metabolized [³H]GA₁ slowly. The major metabolites of [³H]GA₁ in anise were tentatively identified as GA₈-glucoside (24%), GA₈ (15%), GA₁-glucoside (8%) and the ¹⁽¹⁰⁾GA₁-counterpart (2%). Thus, high levels of a GA₁-like substance and a reduced ability to metabolize GA₁ are correlated with the absence of embryo development, while lowered levels of GA₁-like substance and a rapid metabolism of GA₁ into GA₈ and GA-conjugates are correlated with continued embryo development. Exogenous application of GA₃ is known to reduce somatic embryogenesis in carrot cultures; GA₄ was found to have the same effect in anise cultures. Thus, a role (albeit negative) in somatic embryogenesis for a polar, biologically active GA is implied.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GA gibberellin(s) or gibberellin-like substances - GC-RC gas chromatography-radiochromatogram counting - HPLC high-presare liquid chromatography - Rt retention time - TLC thinlaver chromatography     

Genetic control of 6-phosphogluconate dehydrogenase (6-PGD) isozymes in cultivated wheat and rye

Summary The 6-phosphogluconate dehydrogenase (6-PGD) zymogram phenotypes of wheat, rye and their aneuploid derivatives were determined. Two genes involved in the production of 6-PGD isozymes were located on chromosome arms CRL (4 RL) and FRL (6 RL) of Imperial rye. On the basis of differential interactions between wheat and rye chromosomes, evidence was obtained that genes located on chromosomes 6 A, 6 BL and 7 BL control 6-PGD isozyme activities in Chinese Spring wheat. The wheat and rye 6-PGD zymogram phenotypes were indicative of homoeologous relationships between rye chromosome 6 RL to wheat chromosomes of group 6, and rye chromosome 4 RL to wheat chromosomes of group 7.     

Taxonomic relations between archaebacteria including 6 novel genera examined by cross hybridization of DNAs and 16S rRNAs

DNAs from 16 species of archaebacteria including 6 novel isolates were hybridized with 16S rRNAs from 7 species representing different orders or groups of the urkingdom of archaebacteria. The yields, normalized for the number of genes per microgram of DNA, and the temperature stabilities of all hybrids were determined and related to each other. A taxonomic tree constructed from such fractional stability data reveals the same major divisions as that derived from comparative cataloging of 16S rRNA sequences. The extreme halophiles appear however as a distinct order besides the three known divisions of methanogens. The methanogens, the halophiles and Thermoplasma form one of two clearly recognizable branches of the archaebacterial urkingdom. The order represented by Sulfolobus and the related novel order Thermoproteales form the other branch. Three novel genera, Thermoproteus, Desulfurococcus and the "stiff filaments" represent three families of this order. The extremely thermophilic methanogen Methanothermus fervidus belongs to the Methanobacteriales. SN1, a methanogen from Italy, appears as another species of the genus Methanococcus. Another novel methanogen, M3, represents a genus or family of the order Methanomicrobiales.     

Crystallization,crystal structure analysis and molecular model of the third domain of Japanese quail ovomucoid,a Kazal type inhibitor

The third domain of Japanese quail ovomucoid, a Kazal type inhibitor, has been crystallized and its crystal structure determined at 2.5 Å resolution using multiple isomorphous replacement techniques. The asymmetric unit contains four molecules. In the crystal the molecules are arranged in two slightly different octamers with approximate D4 symmetry. The molecules are held together mainly by interactions of the N-terminal residues, which form a novel secondary structural element, a β-channel.The molecule is globular with approximate dimensions 35 Å × 27 Å × 19 Å. The secondary structural elements are a double-stranded anti-parallel β-sheet of residues Pro22 to Gly32 and an α-helix from Asn33 to Ser44. The reactive site Lys18-Asp19 is located in an exposed loop. It is close to Asn33 at the N terminus of the helical segment. The polypeptide chain folding of ovomucoid bears some resemblance to other inhibitors in the existence of an anti-parallel double strand following the reactive site loop.     

Guidelines for safety tests on insect viruses

Guidelines for testing the safety of insect viruses for use as insecticides have been formulated in the light of the recent decade's experience and accumulation of knowledge. In the familyBaculoviridae, the nuclear polyhedrosis and granulosis viruses of Lepidoptera and sawflies (Hymenoptera) are a particularly homogeneous group which have been tested very extensively, without any evidence of hazard to man and vertebrates. It is considered, therefore, that data for viruses already tested can be used as evidence for the safety of a new virus in this group, so that only a limited series of mandatory tests are necessary on the new virus product itself. Other viruses may require the full range of tests, which include data on the identification of the virus; nature of the formulation; biological properties; manufacture; quality control; application; efficacy; residues; infectivity, toxicity and allergenicity in mammals (involving short, intermediate and long term application to various mammalian species by a variety of routes, and observation of humans who have handled the virus) and on wildlife (bees, important predators and parasites of target species, earthworms, fish and birds). It is recommended that additional non-mandatory research should be undertaken on subjects such as the behaviour of the viral genome, improved methods of identifying viruses and of testing safety.     

Your son is cured now; You may take him home

While responding to a question on medical errors in an in-depth interview, a physician told a story about a medical error. The story revealed his silent involvement in the evolution of the error. His response is presented as a text requiring interpretation. Fine details of his manner of speaking are displayed in order to disclose what he said and what it meant. In interpreting the text, phenomenological and sociolinguistic methods are used.