Effect of glycerol on plasmid transfer in genetically competent Haemophilus influenzae

Summary The small plasmid pAT4 transformed at characteristically low frequencies those competent Haemophilus influenzae Rd strains that had no DNA homology with this plasmid. Transformation was increased up to 100 times, however, when the recipient cells were exposed to 30% glycerol before plating for transformants. Expression of plasmid resistance markers was then immediate. Ultraviolet irradiation experiments indicated that this large increase was due to release by the glycerol of double-stranded plasmid molecules, presumably from transformasomes. Several other plasmids exhibited the same phenomenon. Dimethylsulfoxide also stimulated plasmid transformation but lysolecithin and high concentrations of NaCl or glucose were ineffective. Glycerol did not increase the efficiency of transformation by either chromosomal DNA or linearized plasmid DNA.     

A new dimension to observations in minirhizotrons: A stereoscopic view on root photographs

Summary With a stereoscope, as used for the inspection of aerial photographs, sequential photographs of roots obtained by the endoscope method from minirhizotrons can yield much more information than hitherto. A series of photographs shows that most of the roots seen in a minirhizotron in grassland grew on the surface of the lexan tube, while there was a gap between the roots and the soil. Decay of the extensive root hair zones around the roots may make new root growth in the gap between rhizotron wall and soil invisible. Some consequences of these observations for the endoscope method are discussed.     

The Cladocera and Copepoda of the Alta water-course, Northern Norway

Cladocera and Copepoda fauna, from ten lakes in the Alta water-course,northern Norway, have been collected and investigated. A totalof 42 species (34 Cladocera and 8 Copepoda) were recorded. Thenumber of Cladoceran species is high when compared with thatregistered for other areas of similar latitude, and Cladoceranspecies abundance is also greater than that reported for otherregions of northern and central Scandinavia. In addition, themean number of planktonic species present at any given timein the lakes (4.9 Cladocera and 3.4 Copepoda) was comparativelyhigh. Eight species have never been recorded as existing farthernorth than the Alta water-course, Three other species have beenrecorded at higher latitudes in North America, but not in Eurasia.Several species, of which there are only a few published records,arc rare in northern Scandinavia, and nine species were notconsidered by Illies (1978), as existing in the region of thepresent study.     

Phytoplankton productivity in turbid waters

Many of the freshwater areas in the world are turbid, due tosuspended inorganic particles. The euphotic depth of the shallowturbid impoundment, Wuras Dam, varies between 0.3–1.3m. This results in a compressed production profile where accuratemeasurements become difficult. Tubes of various lengths havebeen used and usually render higher rates, when compared todiscrete bottle incubations. A tube the depth of the euphoticzone confines the phytoplankton in the light and the rates measuredrepresent the maximal possible under the prevailing conditions.Longer tubes include an aphotic portion and give an idea ofthe magnitude of respiration losses. The depth of the mixinglayer appears to be especially important in turbid systems asthe time spent in the dark, relative to the light is of greatimportance and may be the most important regulating factor insuch waters. ^*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP), Second International Workshop heldat the National Oceanographic Institute, Haifa, Israel in April–May1984.     

HERSIM: a microcomputer program designed to compute the limits of conversion for real homogeneous isothermal enzymic reactors

HERSIM is a program written in BASIC designed to aid the investigatorinterested in determining the substrate conversion in a realhomogeneous isothermal enzymic reactor, for various kineticequations. The program runs after tracer data relative to aDirac impulse to the reactor have been entered, and computesthe two limits of real conversion: total segregation and maximummixedness. The kinetic constants of the reacting system areinput as data, and the variation of conversion with reactortemperature between given limits is computed as accurately asrequested. Received on November 6, 1986; accepted on March 4, 1987     

Water economy in bird nests

Summary Nest humidity ( ) under an incubating bantam hen was measured at ambient ranging from 1.3 to 25.0 mmHg. Weight loss of eggs was recorded in clutches of varying size. Nest and ambient were also measured in wild incubating willow ptarmigan nests in dry and wet habitats.Nest increased linearly with ambient in a way predictable on the assumption that the water vapour conductance ( ) of brood patch skin, plumage and eggs were constant and independent of ambient . Nest was also dependent of clutch size. Egg dehydration was quantitatively predicted from measured values and the laws of diffusion.Our findings confirm earlier conclusions that the adult bird does not actively regulate nest at varying ambient . Birds can presumably achieve appropriate egg dehydration by a strategy combining nest site, nest construction, egg shell conductance and incubation behaviour which meets the requirements of their breeding climate.Abbreviations water vapur pressure - water vapur conductance - water flux     

A new non-equilibrium enzyme linked immunosorbent assay for a glycogen-derived urinary tetrasaccharide

The tetrasaccharide, Glc1-6Glc1-4Glc1-4Glc, denoted (Glc)₄, is a limit dextrin formed by amylolytic degradation of glycogen. In order to evaluate the possible clinical importance of (Glc)₄ excretion as an indicator of certain physiological and pathological conditions, we have developed a new rapid and inexpensive immunoassay using a monoclonal antibody raised against (Glc)₄ glycosidically-linked to a carrier protein. As the antibody is highly specific, it can be used to measure native (Glc)₄ directly, without the chemical reduction step required in previous methods. A new type of non-equilibrium ELISA inhibition test was developed based on the capacity of free (Glc)₄ to decrease initial rates of antibody binding to (Glc)₄-coated microtiter wells. The method is highly reproducible and is as sensitive and accurate as the gas chromatography method or radioimmunoassay used previously.Abbreviations (Glc)₄ Glc1-6Glc1-4Glc1-4Glc - KLH keyhole limpet hemacyanin - BSA bovine serum albumin - PEG polyethylene glycol     

Comparison of the enthalpy state of vesicles of different size by their interaction with α-lactalbumin

The characteristics of small unilamellar, large unilamellar and large multilamellar vesicles of dimyristoylphosphatidylcholine and their interaction with α-lactalbumin are compared at pH 4. (1) By differential scanning calorimetry and from steady-state fluorescence anisotropy data of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene it is shown that the transition characteristics of the phospholipids in the large unilamellar vesicles resemble more those of the multilamellar vesicles than of the small unilamellar vesicles. (2) The size and composition of the lipid-protein complex formed with α-lactalbumin around the transition temperature of the lipid are independent of the vesicle type used. Fluorescence anisotropy data indicate that in this complex the motions of the lipid molecules are strongly restricted in the presence of α-lactalbumin. (3) The previous data and a comparison of the enthalpy changes, $\text{ΔH}$, of the interaction of the three vesicle types with α-lactalbumin allow us to derive that the enthalpy state of the small unilamellar vesicles just below 24°C is about 24 kJ/mol lipid higher than the enthalpy state of both large vesicle types at the same temperature. The abrupt transition from endothermic to exothermic $\text{ΔH}$ values around 24°C for large vesicles approximates the transition enthalpy of the pure phospholipid     

Recovery of proteins on a milligram scale from polyacrylamide electrophoresis gels,exemplified by purification of a retinol-binding protein

An apparatus suitable for the recovery of proteins from polyacrylamide gels on a milligram scale by displacement electrophoresis (isotachophoresis) is described along with a buffer system that is suitable for this purpose with most proteins. The technique is illustrated by the recovery of a protein from a 15% polyacrylamide gel. The recovery was almost quantitative and the eluted protein showed little contamination upon quantitative amino acid analysis and automatic Edman degradation.     

Caprolactam,a light-promoted growth inhibitor in sunflower seedlings

A neutral growth inhibitor, isolated from methanolic extracts of sunflower seedlings, was characterized by spectral data as caprolactam. Light-grown se