Close linkage between X-linked ectodermal dysplasia and a cloned DNA sequence detecting a two allele restriction fragment length polymorphism in the region Xp11-q12

Summary EDA (ectodermal dysplasia, anhidrotic) is an X-linked recessive disorder characterized by hypohidrosis, hypoor anodontia, and hypotrichosis. A possible linkage between the gene for EDA and a number of restriction fragment length polymorphisms (RFLPs) spread over the X chromosome was investigated in two Danish families segregating EDA. No recombination between the gene for EDA and our probe pTAK8, which detects a two allele polymorphism in the region Xp11-q12, was found in nine informative meiotic events (seven of which are phase known), giving a maximal lod score of 2.41 at a recombination fraction of 0.00. This juxtacentromeric location of the gene for EDA agrees well with the linkage data obtained with the other markers used in this study.     

The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver

Summary Using a target simulator three serotine bats,Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3).In a subsequent experiment the phantom target was masked with white noise (N_o) with a spectrum level of –113 dB re. 1 Pa·Hz^–1/2. The thresholds were increased by 7–14 dB. Energy density (S) of a single pulse was measured and used to estimate S/N_o, which ranged from 36–49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/N_o of ca. 1–2 dB. Since the bats require 40–50 dB higher S/N_o (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation).Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.Abbreviations C clutter - Nbw noise in a specified bandwidth - No noise in i Hz bandwidth - peSPL peak equivalent sound pressure level - S signal energy - SD standard deviation - Y/N Yes/No psychometry - 2AFC two alternative forced choice psychometry     

Feeding and growth of larval herring,Clupea harengus,in relation to density of copepod nauplii

Synopsis Feeding and growth rates of 1–3 wk old herring larvae from four different stocks were compared in laboratory experiments (8°C). For most of the larval groups, feeding rate was saturated at nauplii (Acartia tonsa, nauplii stages 3–5) densities over 301^–1 (5 g d.w. 1^–1). Specific growth rate increased asymptotically with nauplii density, and reached about 6% d^–1 at densities over 120 nauplii 1^–1. The growth rates attained in the laboratory were similar to field measured growth rates of similarly aged herring larvae at comparable food densities. Since food particles were homogenously distributed in the laboratory tanks, patches of dense plankton concentrations are, thus, apparently not necessary for larval growth and survival in the sea. Growth efficiency differed between larval groups, with large sized larvae being the most efficient in transforming ingested matter into growth. The difference probably relates to different sizes rather than to the different geographical origins of the larvae.     

Light-temperature interactions in the control of photosynthesis in Antarctic phytoplankton

Summary During October/November 1983 photosynthetic responses of natural phytoplankton from the Scotia Sea and Bransfield strait to light and temperature were examined in incubators. Both assimilation numbers at saturating light levels and the slopes of the light-limited portions of the photosynthesis versus irradiance curves were smaller than in algae from lower latitudes. However, both parameters increased significantly with rising temperatures. Light-saturated photosynthesis on the average exhibited a Q₁₀-value of ca. 4.2 between-1.5°C and +2°C. Light-limited photosynthesis between-1.5°C and +5°C rose at a rate corresponding to a Q₁₀-value of roughly 2.6. Above +5°C, temperature enhancement of both light-saturated and light-limited photosynthetic rates was minimal or absent. Our results suggest that under extremely low temperatures light-limited photosynthetic rates become temperature-dependent due to changes in maximum quantum yields.     

Localization of the neuronal cell adhesion molecule D2-protein in explant cultures of dorsal root ganglia by use of the colloidal-gold immunocytochemical technique

Summary The localization of the neuronal cell adhesion molecule (N-CAM), D2-protein, in explant cultures of rat dorsal root ganglia was investigated at the electron microscope level by the use of 17-nm-diameter colloidal gold particles coated with swine anti-rabbit immunoglobulin molecules. The minimum amount of IgG needed to coat the gold particles and the pH optimal for coating were both determined. Immunocytochemical studies of cultures revealed the binding of gold particles to the neuronal plasma membrane, especially on neuritic processes. Schwann cells were not labeled, and the level of unspecific background staining was very low.     

Inhibition of exogenous NADH oxidation in plant mitochondria by chlorotetracycline in the presence of calcium ions

Chlorotetracycline inhibits the uncoupled oxidation of exogenous NADH by Jerusalem artichoke (Helianthus tuberosus L.) mitochondria extensively (over 80%) and rapidly (inhibition complete in 10 s) in the presence of added Ca²⁺. Half-maximal inhibition is observed at 15 μM chlorotetracycline in the presence of 2 mM Ca²⁺. The oxidation of succinate is only affected marginally by chlorotetracycline plus Ca²⁺. The inhibition of NADH oxidation and the fluorescence of CTC are well correlated. Mn²⁺ is the only other cation which shows an (increased) inhibition in the presence of chlorotetracycline. The inhibition by Ca²⁺ and chlorotetracycline disappears at acid pH, and the pH optimum in their presence is 6.4. The inhibition caused by other lipid-soluble Ca²⁺-chelators is not reversible or is enhanced by the addition of excess Ca²⁺. In contrast, inhibition caused by relatively water-soluble chelators is completely reversed by added Ca²⁺. It is suggested that a neutral 1:2 complex is formed between Ca²⁺ and chlorotetracycline which can substitute for Ca²⁺ bound at sites in the lipophilic phase of the inner mitochondrial membrane, which are essential for the activity of the external NADH dehydrogenase.     

Production estimates of the benthic invertebrate community in a small Danish stream

Quantitative samples were used to investigate density, biomass and annual production of the benthic invertebrate fauna in a small Danish stream. Forty-eight taxa were found and the total invertebrate densities varied from 3 810 m^?2 in July to 20 040 m^?2 in December. The total mean annual biomass of the invertebrate fauna was 6.1 g ash-free dry wt m^?2. The annual production of the invertebrates was estimated from their mean annual biomass and their annual P/B ratio. Production of the primary consumers (herbivores and detritivores) was 21.4 g ash-free dry wt m^?2 y^?1 and of secondary consumers (carnivores) 1.1 g m^?2 y^?1. The amount of invertebrate production available to the trout population and the importance of the species as food for trout are discussed.     

Determination of growth-limiting nutrients for red species of Oscillatoria and two ‘oligotrophic’ diatoms

Laboratory batch experiments with dilute phytoplankton communities were carried out to determine growth-limiting nutrients and the degree of growth limitation for Asterionella formosa, Hass., Tabellaria fenestrata (Lyngb.) Kütz. and red species of Oscillatoria under specific temperature and light conditions. Water samples from five Norwegian lakes with average epilimnetic total phosphorus concentrations ranging from 5 to 30 µg P per 1 were investigated. Both enrichment and transplant experiments were carried out. In samples from the most oligotrophic lakes (Lake Randsfjorden and Lake Tyrifjorden) phosphorus was found to be the growth-limiting nutrient. In samples from Lake Mjøsa silicate was also growth-limiting for the diatoms, while nitrogen could be limiting for both asterionella and Oscillatoria from Lake Steinsfjorden. Phosphorus was often the only limiting nutrient determined for Oscillatoria in Lake Gjersjøen (the most eutrophic of the lakes). In samples from this lake, however, Asterionella was also growth-limited directly or indirectly as a result of high (pH > 9). This was also found for Asterionella and Tabellaria from lake Mjøsa by means of transplant experiments. Oscillatoria from Lake Gjersjøen could not grow in filtered water from Lake Mjøsa but obtained maximum growth rate after addition of phosphate and chelated iron in combination.     

The Ca2+ permeability of sarcoplasmic reticulum vesicles II. Ca2+ efflux in the energized state of the calcium pump

Ca²⁺ efflux from sarcoplasmic reticulum vesicles was studied by measurements of net Ca²⁺ uptake, ⁴⁵Ca²⁺ flux and hydrolysis of energy-rich phosphate. The maximal Ca²⁺ uptake capacity (150–200 nmol/mg protein at pH 6.7, 10 mM MgCl₂ and μ=0.26) was independent of the nature and concentration of the energy-donating substrate (ATP or carbamyl phosphate) and of temperature (15–35°C), suggesting coupling between influx and efflux of Ca²⁺. In the presence of high concentrations of ATP, this efflux of Ca²⁺ was much higher than the passive Ca²⁺ permeation, measured after ATP or Ca²⁺ depletion of the reaction medium. Ca²⁺ efflux was imperceptible at vesicle filling levels below 35–40 nmol Ca²⁺/mg protein, and uncorrelated to the inhibition of the Ca²⁺-ATPase by high intravesicular Ca²⁺ concentrations. Analysis of the data indicated that Ca²⁺ efflux under our conditions probably is associated with one of the Ca²⁺-ATPase partial reactions occurring after dephosphorylation, rather than with a reversal of the Ca²⁺ translocation step in the phosphorylated state of the enzyme. Furthermore, passive Ca²⁺ permeation may be concurrently reduced during the enzymatically active state. It is proposed that both Ca²⁺ efflux and passive Ca²⁺ permeation (Ca²⁺ outflow) proceed via the same channels which are closed (occluded) during part of the Ca²⁺-ATPase reaction cycle.     

Physical conditions of propagation media and their influence on the rooting of cuttings

Summary The formation and subsequent growth of roots by cuttings of poinsettia, hydrangea, rose and azalea in various propagation media, Jiffy-7, Jiffy-9 and Grodan under different conditions of aeration was investigated. The interrelationships of the effects of air content of the media, temperature and light intensity on the rooting of poinsettia cuttings was also studied.With low air contents (0 cm moisture tension) in the propagation media the formation and growth of roots was strongly inhibited. The rooting performance of rose appeared to be less affected by the poor aeration. Increasing air content improved rooting but best results were obtained at moisture tensions of 4 to 8 cm. Rooting seems to be better correlated with oxygen diffusion rate (ODR) than with air content.For poinsettia cuttings the optimum temperature for rooting was 24 to 28°C. At low temperatures rooting was delayed while at higher temperatures it was almost completely inhibited. Callus formation increased with temperature but decreased with increasing moisture tension. Conditions which induced large callus formation inhibited root formation.High light intensity during rooting reduced overall rooting performance and the inhibition was most pronounced in conjunction with high moisture tensions.Report No. 255.