Rotational motions in myoglobin assessed by carbon 13 relaxation measurements at two magnetic field strengths.

Proton-decoupled Fourier transform nuclear magnetic resonance spectroscopy of natural abundance 13C was used to obtain spectra of cyanoferrimyoglobin of sperm whale (Physeter catadon) at 14.1 and 23.5 kG. Comparison of the spin lattice relaxation times at these two field strengths allowed the unambiguous assignment of a rotational correlation time of 22 plus or minus 5 ns for the alpha carbon resonances. The spin lattice relaxation time value for a major band attributable to aromatic carbon atoms also corresponded to a single correlation time, attributable to over-all tumbling of the molecule. Certain narrower resonances reflect other modes of rotational motion in addition to the over-all tumbling. Observations of nuclear Overhauser enhancement and line widths accord with these conslusions.     

Nutrients and phytoplankton primary production in the marine tidal Oosterschelde estuary (The Netherlands)

In a shallow marine tidal area, the eastern part of Oosterschelde estuary in the S.W. Netherlands, phytoplankton primary production amounted to 176–338 g C.m^?2.y^?1 during the period 1981–1985. The influence of nutrient concentrations on the phytoplankton primary production is discussed. Phosphate and inorganic nitrogen generally were amply available. Import of inorganic nitrogen into the basin was shown and an intense delivery of ammonia by zoobenthos was suggested. Nitrate was considered to be slightly influenced by phytoplankton consumption and mainly by nitrate reduction at the bottom. Silicate may have played a limiting role in phytoplankton primary production. The first phytoplankton bloom in spring (diatom bloom) always terminated when silicate concentration decreased below K_s values. Further on in 1983 and 1984 both primary production and chlorophyll curves showed a dip when silicate was not available. The influence of available light on the primary production was demonstrated during situations with a low extinction coefficient when primary production reached maximum values. Further on during 1985 the spring bloom occurred already in March when winter extinction coefficients were lower than during preceding winters. Long term production studies are necessary to understand the extreme fluctuations of annual production patterns in relation to the prevailing environmental conditions.     

Temperature dependence of energy transfer from the long wavelength antenna BChl-896 to the reaction center in Rhodospirillum rubrum,Rhodobacter sphaeroides (w.t. and M21 mutant) from 77 to 177K,studied by picosecond absorption spectroscopy

Decay of the bacteriochlorophyll excited state was measured in membranes of the purple bacteria Rhodospirillum (R.) rubrum, Rhodobacter (Rb.) sphaeroides wild type and Rb. sphaeroides mutant M21 using low intensity picosecond absorption spectroscopy. The excitation and probing pulses were chosen in the far red wing of the long wavelength absorption band, such that predominantly the minor antenna species B896 was excited. The decay of B896 was studied between 77 and 177K under conditions that the traps were active. In all species the B896 excited state decay is almost temperature independent between 100 and 177K, and probably between 100 and 300 K. In this temperature range the decay rates for the various species are very similar and close to 40 ps. Below 100 K this rate remains temperature independent in Rb. sphaeroides w. t. and M21, while in R. rubrum a steep decrease sets in. An analysis of this data with the theory of nuclear tunneling indicates an activation energy for the final transfer step from B896 to the special pair of 70cm^-1 for R. rubrum and 30cm^-1 or less for Rb. sphaeroides.Abbreviations B880 and B896 the main and long wavelength bacteriochlorophyll's of the LH-1 antenna - RC reaction centre - P special pair in the RC     

The Apectodinium acme and terrestrial discharge during the Paleocene-Eocene thermal maximum: new palynological, geochemical and calcareous nannoplankton observations at Tawanui, New Zealand

Manifestations of profound perturbations in biogeochemical systems during the Paleocene-Eocene thermal maximum (PETM) include a prominent global negative δ¹³C and a pronounced increase in the relative abundance of dinoflagellate cysts (dinocysts) assigned to the genus Apectodinium. While motile representatives of Apectodinium were most likely thermophilic and heterotrophic, the underlying causes of this dinoflagellate response are not well understood. Here we provide new insight by examining the palynology, chemistry and calcareous nannoplankton across the PETM in a continental slope section at Tawanui, New Zealand. Across the PETM, marked changes in the relative abundance of Apectodinium vary antithetically with significant changes in the δ¹³C of carbonate and organic matter. In general, the high relative abundance of Apectodinium relates to enhanced concentrations of dinocysts, signifying a ‘bloom’ of Apectodinium in surface waters during the PETM. Changes in Apectodinium and δ¹³C records correspond to variations in many other parameters, including a smaller negative shift in bulk carbonate δ¹³C than expected, increased terrestrial palynomorphs, elevated TOC and C/N ratios, lower carbonate contents, higher SiO₂ and Al₂O₃ contents, and lower Si/Al ratios. All of these variations can be explained by an increase in delivery of terrigenous material to the continental margin. A peak in the relative abundance of Glaphyrocysta dinocysts at the onset of the PETM may indicate greater down slope transport of neritic material. Changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the PETM. The combined results show that Apectodinium-dominated assemblages, global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at Tawanui. A sudden and massive carbon injection to the ocean-atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the PETM. We further suggest that these inputs caused the Apectodinium acme by elevating primary productivity in marginal seas.     

Vibration Signal Behavior of Waggle-dancers in Swarms of the Honey Bee,Apis mellifera (Hymenoptera: Apidae)

We hypothesize two functions of the vibration signal (dorsal ventral abdominal vibration = DVAV) during swarming in honey bees: 1. it enhances recruitment to the specific sites advertised by the waggle dancers which also perform the vibration signal; and 2. it acts as a nonspecific modulatory signal to stimulate activity in other bees. The stimulation of activity invoked by the second hypothesis might include increasing nest-site scouting and dance following early in the house-hunting process or rousing quiescent bees to prepare them for lift-off late in the process, or both. In studies of neotropical African bee swarms in Costa Rica and European bees in California we tested these hypotheses by looking for associations between production of vibration signals by nest-site recruiters and site attractiveness (indicated by which site was ultimately chosen and by distance from the swarm since swarms may have a distance preference). Overall, bees dancing for the chosen sites performed vibration signals to the same extent as those dancing for the other sites. There were no distance differences between sites whose scouts did and did not vibrate other bees. These results are inconsistent with the hypothesis that the vibration signal enhances recruitment to especially high quality sites and they support the hypothesis that it plays a general excitatory role in the context of house hunting by swarming bees.     

Four-parameter white blood cell differential counting based on light scattering measurements

Measurement of the depolarized orthogonal light scattering in flow cytometry enables one to discriminate human eosinophilic granulocytes from neutrophilic granulocytes. We use this method to perform a four-parameter differential white blood cell analysis. A simple flow cytometer was built equipped with a 5-mW helium neon laser that measures simultaneously four light scattering parameters. Lymphocytes, monocytes, and granulocytes were identified by simultaneously measuring the light scattering intensity at angles between 1.0 degrees and 2.6 degrees and angles between 3.0 degrees and 11.0 degrees. Eosinophilic granulocytes were distinguished from neutrophilic granulocytes by simultaneous measurement of the orthogonal and depolarized orthogonal light scattering. Comparison of a white blood cell differentiation of 45 donors obtained by the Technicon H-6000 and our instrument revealed good correlations. The correlation coefficients (r2) found were: 0.99 for lymphocytes, 0.76 for monocytes, 0.99 for neutrophilic granulocytes, and 0.98 for eosinophilic granulocytes. The results demonstrate that reliable white blood cell differentiation of the four most clinically relevant leukocytes can be obtained by measurement of light scattering properties of unstained leukocytes.     

Auditory short-term memory behaves like visual short-term memory

Are the information processing steps that support short-term sensory memory common to all the senses? Systematic, psychophysical comparison requires identical experimental paradigms and comparable stimuli, which can be challenging to obtain across modalities. Participants performed a recognition memory task with auditory and visual stimuli that were comparable in complexity and in their neural representations at early stages of cortical processing. The visual stimuli were static and moving Gaussian-windowed, oriented, sinusoidal gratings (Gabor patches); the auditory stimuli were broadband sounds whose frequency content varied sinusoidally over time (moving ripples). Parallel effects on recognition memory were seen for number of items to be remembered, retention interval, and serial position. Further, regardless of modality, predicting an item's recognizability requires taking account of (1) the probe's similarity to the remembered list items (summed similarity), and (2) the similarity between the items in memory (inter-item homogeneity). A model incorporating both these factors gives a good fit to recognition memory data for auditory as well as visual stimuli. In addition, we present the first demonstration of the orthogonality of summed similarity and inter-item homogeneity effects. These data imply that auditory and visual representations undergo very similar transformations while they are encoded and retrieved from memory.