Surface areas,lengths and volumes of Picea abies (L.) Karst. needles: determination,biological variability and effect of environmental factors

Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm²) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm³) by needle volume = 0.208 x projected needle area ^1.353 (r = 0.969).     

THE SEPARATION OF DIFFERENT CELL CLASSES FROM LYMPHOID ORGANS : III. The Purification of Erythroid Cells by pH-Induced Density Changes

1. Mammalian erythrocytes swell as the pH of the isotonic suspending medium is lowered, as a direct consequence of the specialized permeability properties of the erythrocyte membrane. Lymphocytes and granulocytes from a variety of sources did not exhibit this property. 2. The behaviour of mouse bone marrow erythroid cells at various stages of differentiation was studied by using a change in buoyant density with pH as an index of swelling. The ability to swell with a pH drop was acquired while the cell was still nucleated. All non-nucleated cells showed swelling. Most small erythroblasts shared this property, whereas most large erythroblasts did not. 3. The density shift with pH was used to provide a purification scheme specific for erythroid cells. The bone marrow cells were first centrifuged to equilibrium in an isotonic albumin density gradient at neutral pH. Regions of the gradient containing the erythroid cells were collected, and the cells were recovered and redistributed in an albumin gradient at acid pH. The erythroid cells showed a specific density shift which removed them from contaminants. Preparations containing 90–97% erythroblasts were obtained by this technique. 4. Differentiation within the erythroid series was accompanied by a general increase in cell buoyant density at neutral pH. This density increase may have been a discontinuous process, since erythroid cells appeared to form a number of density peaks. 5. The pH shift technique, in association with established density distribution and sedimentation velocity procedures, provides a range of cell separation techniques for biological or biochemical studies of erythroid cell differentiation in the complex cell mixtures in bone marrow or spleen.     

The unusual social organization of the antPachycondyla tridentata (Formicidae,ponerinae)

Colonies of the ponerine antPachycondyla tridentata from Malaysia occur with and without queens. In a total of 7 colonies we found more than 80% of the workers to be mated, irrespective of the presence or absence of queens. This is a hitherto unknown social organisation in ants. Queens and workers competed equally for reproduction. In the colonies investigated several ants were laying eggs. Behavioral observations revealed persistent dominance interactions between colony members. A few ants, but not necessarily a queen, occupied top positions. Removal of the most dominant ants led to a new hierarchy in which subordinate ants with developed ovaries were attacked significantly more frequently than non-reproductive ants. On the average, callows were more aggressive than older subordinate ants, displacing most of the older laying workers in one colony. Nestmate recognition tests revealed that non-reproductive ants were much more aggressive towards foreign ants than were ants with developed ovaries.     

Accumulation of hexoses in leaf vacuoles: Studies with transgenic tobacco plants expressing yeast-derived invertase in the cytosol,vacuole or apoplasm

The subcellular distribution of hexoses, sucrose and amino acids among the stromal, cytosolic and vacuolar compartments was analysed by a nonaqueous fractionation technique in leaves of tobacco (Nicotiana tabaccum L.) wild-type and transgenic plants expressing a yeast-derived invertase in the cytosolic, vacuolar or apoplasmic compartment. In the wild-type plants the amino acids were found to be located in the stroma and in the cytosol, sucrose mainly in the cytosol and up to 98% of the hexoses in the vacuole. In the leaves of the various transformants, where the contents of hexoses were greater than in wild-type plants, again 97–98% of these hexoses were found in the vacuoles. It is concluded that leaf vacuoles contain transporters for the active uptake of glucose and fructose against a high concentration gradient. A comparison of estimated metabolite concentrations in the subcellular compartments of wild-type and transformant plants indicated that the decreased photosynthetic capacity of the transformants is not due to an osmotic effect on photosynthesis, as was shown earlier to be the case in transformed potato leaves, but is the result of a long-term dedifferentiation of tobacco leaf cells to heterotrophic cells.Abbreviations apo-inv tobacco plant with yeast invertase in the apoplasm - Chl chlorophyll - cy-inv tobacco plant with yeast invertase in the cytosol - vac-inv tobacco plant with yeast invertase in the vacuole - WT wild-type tobacco plant The authors thank A. Großpietsch for her able technical assistance. This work has been supported by the Bundesminister für Forschung und Technologie.     

A family of modular type mannuronan C-5-epimerase genes controls alginate structure in Azotobacter vinelandii

The ToxR protein is a transmembrane protein that regulates the expression of several virulence factors of Vibrio cholerae. Previous analysis of fusion proteins between ToxR and alkaline phosphatase (ToxR-PhoA) suggested that ToxR was active as a dimer. In order to determine whether dimerization of the ToxR periplasmic domain was essential for activity, this domain was replaced by monomeric and dimeric protein domains. Surprisingly, PhoA (dimeric), β-lactamase (monomeric, ToxR–Bla), or the leucine zipper of GCN4 (dimeric, ToxR-GCN4-M) could substitute functionally for the ToxR periplasmic domain. ToxR-GCN4 fusion proteins, in which the ToxR trans-membrane domain was eliminated (ToxR-GCN4-C), were inactive, but an additional fusion protein that contained a heterologous membrane-spanning domain retained activity. Strains containing each of these ToxR fusion proteins were analysed for in vivo colonization properties and response to in vitro growth conditions that are known to affect expression of the ToxR regulon. Strains containing ToxR-GCN4-M and ToxR-Bla responded like wild-type strains to in vitro growth conditions. In the infant-mouse colonization model, strains containing ToxR fusion proteins were all deficient in colonization relative to strains containing wild-type ToxR, and strains containing monomeric ToxR-Bla were most severely outcompeted. These results suggest that, under in vitro conditions, ToxR does not require a dimerized periplasmic domain, but that, under in vivo conditions, the correct conformation of the ToxR periplasmic domain may be more important for function.     

What spectroscopy can still tell us about the secondary structure of bacteriorhodopsin.

The recently published model of the structure of bacteriorhodopsin (bR), developed by fitting the peptide chain to a high-resolution, three-dimensional density map, rules out the existence of transmembrane beta-sheet and provides an accurate estimate of the helix content. The precise geometry of the dihedral angles in the helical regions of the polypeptide cannot yet be specified from the diffraction data, however. Published data on the circular dichroism (CD) spectrum between 190 and 240 nm, and the infrared (IR) spectrum in the amide I band suggest that the helical conformation in bR may be, for the most part, a rather unusual one. The precise structural model, which specifies the number of residues in transmembrane helices, can now be used as an additional constraint in seeking models of the helical conformation that are in quantitative agreement with the CD and IR spectroscopic data. Further spectroscopic measurements can also be used to determine whether there are changes in the unusual dihedral-angle conformation within the helices during the photocycle.