Simultaneous tracking of flagellates in real time by image analysis

The hardware and software components are described to track many flagellates simultaneously in real time. The technique is based on on-line digitization of four frames taken at 80 ms intervals and stored in a specialized video memory. The outline and position of each organism are determined by chain coding and followed through the recorded series of images. The movement vectors of all organisms tracked are stored in the form of deviation angles from a predefined stimulus (light or gravity) direction and the distance each organism has moved in the time interval determined by the hardware clock of the computer. Subsequent programs allow one to determine circular histograms of movement directions and velocities in dependence of the movement direction. Examples of several orientation patterns are given for both photoorientation and gravitaxis in the dinoflagellate, Peridinium gatunense.Supported by grants from the Deutsche Forschungsgemeinschaft (SFB 305, Marburg and Ha 985/6-1, Erlangen)     

A computerized plankton counter

A portable computerized plankton counting system is presented, which has the potential to enumerate 255 different species per sample. The software is used to count phytoplankton samples and produce summary data. The hardware allows the results to be reproduced in the form of a hardcopy, stored on a cassette tape, or transferred to a larger computer for analysis.     

Mites as Selective Fungal Carriers in Stored Grain Habitats

Mites are well documented as vectors of micromycetes in stored products. Since their vectoring capacity is low due to their small size, they can be serious vectors only where there is selective transfer of a high load of specific fungal species. Therefore the aim of our work was to find out whether the transfer of fungi is selective. Four kinds of stored seeds (wheat, poppy, lettuce, mustard) infested by storage mites were subjected to mycological analysis. We compared the spectrum of micromycete species isolated from different species of mites (Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, Caloglyphus rhizoglyphoides and Cheyletus malaccensis) and various kinds of stored seeds. Fungi were separately isolated from (a) the surface of mites, (b) the mites' digestive tract (= faeces), and (c) stored seeds and were then cultivated and determined. The fungal transport via mites is selective. This conclusion is supported by (i) lower numbers of isolated fungal species from mites than from seeds; (ii) lower Shannon–Weaver diversity index in the fungal communities isolated from mites than from seeds; (iii) significant effect of mites/seeds as environmental variables on fungal presence in a redundancy analysis (RDA); (iv) differences in composition of isolated fungi between mite species shown by RDA. The results of our work support the hypothesis that mite–fungal interactions are dependent on mite species. The fungi attractive to mites seem to be dispersed more than others. The selectivity of fungal transport via mites enhances their pest importance.     

A memory system in the monkey

A neural model is presented, based largely on evidence from studies in monkeys, postulating that coded representation of stimuli are stored in the higher-order sensory (i.e. association) areas of the cortex whenever stimulus activation of these areas also triggers a cortico-limbo-thalamo-cortical circuit. This circuit, which could act as either an imprinting or rehearsal mechanism, may actually consist of two parallel circuits, one involving the amygdala and the dorsomedial nucleus of the thalamus, and the other the hippocampus and the anterior nuclei. The stimulus representation stored in cortex by action of these circuits is seen as mediating three different memory processes: recognition, which occurs when the stored representation is reactivated via the original sensory pathway; recall, when it is reactivated via any other pathway; and association, when it activates other stored representations (sensory, affective, spatial, motor) via the outputs of the higher-order sensory areas to the relevant structures.     

Release of small transmitters through kiss-and-run fusion pores in rat pancreatic beta cells

Exocytosis of secretory vesicles begins with a fusion pore connecting the vesicle lumen to the extracellular space. This pore may then expand or it may close to recapture the vesicle intact. The contribution of the latter, termed kiss-and-run, to exocytosis of pancreatic beta cell large dense-core vesicles (LDCVs) is controversial. Examination of single vesicle fusion pores demonstrated that rat beta cell LDCVs can undergo exocytosis by rapid pore expansion, by the formation of stable pores, or via small transient kiss-and-run fusion pores. Elevation of cAMP shifted LDCV fusion pore openings to the transient mode. Under this condition, the small fusion pores were sufficient for release of ATP, stored within LDCVs together with insulin. Individual ATP release events occurred coincident with amperometric "stand alone feet" representing kiss-and-run. Therefore, the LDCV kiss-and-run fusion pores allow small transmitter release but likely retain the larger insulin peptide. This may represent a mechanism for selective intraislet signaling.     

Apple II software for M13 shotgun DNA sequencing.

A set of programs is presented for the reconstruction of a DNA sequence from data generated by the M13 shotgun sequencing technique. Once the sequence has been established and stored other programs are used for its analysis. The programs have been written for the Apple II microcomputer. A minimum investment is required for the hardware and the software is easily interchangeable between the growing number of interested researchers. Copies are available in ready to use form.     

The development of spaceflight experiments with Arabidopsis as a model system in gravitropism studies

Experiments with Arabidopsis have been developed for spaceflight studies in the European Space Agency's Biorack module. The Biorack is a multiuser facility that is flown on the United States Space Shuttle and serves as a small laboratory for studying cell and developmental biology in unicells, plants, and small invertebrates. The purpose of our spaceflight research was to investigate the starch-statolith model for gravity perception by studying wild-type (WT) and three starch-deficient mutants of Arabidopsis. Since spaceflight opportunities for biological experimentation are scarce, the extensive ground-based testing described in this paper is needed to ensure the success of a flight project. Therefore, the specific aims of our ground-based research were: (1) to modify the internal configuration of the flight hardware, which originally was designed for large lentil seeds, to accommodate small Arabidopsis seeds; (2) to maximize seed germination in the hardware; and (3) to develop favorable conditions in flight hardware for the growth and gravitropism of seedlings. The hardware has been modified, and growth conditions for Arabidopsis have been optimized. These experiments were successfully flown on two Space Shuttle missions in 1997.     

Internal representations for associative memory

We describe a class of feed forward neural network models for associative content addressable memory (ACAM) which utilize sparse internal representations for stored data. In addition to the input and output layers, our networks incorporate an intermediate processing layer which serves to label each stored memory and to perform error correction and association. We study two classes of internal label representations: the unary representation and various sparse, distributed representations. Finally, we consider storage of sparse data and sparsification of data. These models are found to have advantages in terms of storage capacity, hardware efficiency, and recall reliability when compared to the Hopfield model, and to possess analogies to both biological neural networks and standard digital computer memories.     

Database on the structure of small ribosomal subunit RNA.

The Antwerp database on small ribosomal subunit RNA now offers more than 6000 nucleotide sequences (August 1996). All these sequences are stored in the form of an alignment based on the adopted secondary structure model, which is corroborated by the observation of compensating substitutions in the alignment. Besides the primary and secondary structure information, literature references, accession numbers and detailed taxonomic information are also compiled. For ease of use, the complete database is made available to the scientific community via World Wide Web at URL http://rrna.uia.ac.be/ssu/ .     

Data transfer from Beckman LS 5800 liquid scintillation counters to IBM personal computers

This communication describes a short routine in BASICA for theIBM-PC, written to collect data from a Beckman liquid scintillationcounter. In the form presented here the routine converts incomingbytes into separate lines and saves these lines in a file. Thereare many possible applications for further use of the data inthese files. A few suggestions are given as to the format inwhich data can be stored and how to process these data automaticallyafter all samples have been counted. The only hardware neededis an asynchronous communications adapter for the IBM-PC andan RS232 cable. Received on July 27, 1985; accepted on August 2, 1985     

Enforced unbinding of biomembranes whose mutual adhesion is mediated by a specific interaction

The enforced unbinding of a biomembrane from a rigid substrate whose adhesion is mediated by a specific interaction has been studied theoretically. We argue that the unbinding takes place via motion of the adhesion rim. We account for the release of the elastic energy (stored in the membrane curvature) in the binding-unbinding process and obtain the dissociation constant at the rim. We further deduce an equation of motion for the rim. The solution exhibits an initial phase describing a slow motion followed by a regime of rapid motion and finally breaking of the adhesion. We show that the unbinding force depends on the rate of force application as F(*) approximately equal (F')(beta). When small forces are applied, beta=1/2, while in the case of large forces, beta=1/3.     

The development of spaceflight experiments withArabidopsis as a model system in gravitropism studies

Experiments withArabidopsis have been developed for spaceflight studies in the European Space Agency's Blorack module. The Biorack is a multiuser facility that is flown on the United States Space Shuttle and serves as a small laboratory for studying cell and developmental biology in unicells, plants, and small invertebrates. The purpose of our spaceflight research was to investigate the starch-statolith model for gravity perception by studying wild-type (WT) and three starch-deficient mutants ofArabidopsis. Since spaceflight opportunities for biological experimentation are scarce, the extensive ground-based testing described in this paper is needed to ensure the success of a flight project. Therefore, the specific aims of our ground-based research were: (1) to modify the internal configuration of the flight hardware, which originally was designed for large lentil seeds, to accommodate smallArabidopsis seeds; (2) to maximize seed germination in the hardware; and (3) to develop favorable conditions in flight hardware for the growth and gravitropism of seedlings. The hardware has been modified, and growth conditions forArabidopsis have been optimized. These experiments were successfully flown on two Space Shuttle missions in 1997.     

Statistical Conditional Sampling for Variable-Resolution Video Compression

In this study, we investigate a variable-resolution approach to video compression based on Conditional Random Field and statistical conditional sampling in order to further improve compression rate while maintaining high-quality video. In the proposed approach, representative key-frames within a video shot are identified and stored at full resolution. The remaining frames within the video shot are stored and compressed at a reduced resolution. At the decompression stage, a region-based dictionary is constructed from the key-frames and used to restore the reduced resolution frames to the original resolution via statistical conditional sampling. The sampling approach is based on the conditional probability of the CRF modeling by use of the constructed dictionary. Experimental results show that the proposed variable-resolution approach via statistical conditional sampling has potential for improving compression rates when compared to compressing the video at full resolution, while achieving higher video quality when compared to compressing the video at reduced resolution.     

Qualification of long-stored samples of serum banks for seroepidemiological studies.

Serum samples were tested for antibodies against polio virus and measles virus from two serum banks after having been stored under different conditions for several years. The results are compared with those ones obtained immediately after sampling. Despite of small increases of antibody-negative samples and of small decreases of the titres the suitability of the samples stored could be shown. Special attention should be given to the establishment, e.g. in the framework of Expanded Programme on Immunization of the World Health Organization and in order to study new pathogens unknown to date, and the technical preconditions for that should be planed.     

Preserved vascular reactivity of rat renal arteries after cold storage

In cultured renal tubular cells hypothermia results in cell damage caused by iron-dependent formation of reactive oxygen species. It is unknown whether cold preservation affects function of renal vessels. Rat renal arcuate arteries were stored in a physiological salt solution at 4 degrees C for 24h and compared to control arteries (not stored). To some of the stored arteries the iron chelator 2,2'-dipyridyl was added. Endothelium-independent vasoconstriction was assessed by cumulative concentration-response curves for potassium and phenylephrine in a small vessel myograph. Endothelium-independent vasodilation was assessed with sodium nitroprusside and endothelium-dependent vasodilation with histamine. Cold storage for 24h did not affect vascular reactivity of renal small arteries and no influence of the iron chelator was seen. Since 24h of cold storage considerable damages renal tubular cells both in vitro and after kidney transplantation, these results suggest that renal arteries are less sensitive to cold-induced damage than tubular cells.     

A continuous-flow culture system for organ culture of large explants of adult tissue: effect of oxygen tension on mouse molar periodontium

A modified continuous-flow culture system (CFCS) was developed to maintain large explants of periodontium from adult mouse in organ culture. The culture medium was stored in a reservoir outside of the incubator, pumped via polyvinyl tubing into small glass culture chambers that were placed in the oxygenator and then collected in a waste flask. Medium was analyzed for pO2, pCO2 and pH during the culture period. Three-molar and single-molar explants of periodontium were maintained for 48 hr in the CFCS at two different pO2 ranges: 100 to 120 mm Hg and 400 to 420 mm Hg. [3H]Proline was added 24 hr prior to sacrifice. Light-microscope morphological and radioautographic observations suggested that cell viability and incorporation of [3H]proline, probably into newly synthesized protein, increased with an increase in pO2 and was related to a pO2 gradient extending from the periphery to the center of the explants.     

A dynamic, cytoplasmic triacylglycerol pool in enterocytes revealed by ex vivo and in vivo coherent anti-Stokes Raman scattering imaging

The absorptive cells of the small intestine, enterocytes, are not generally thought of as a cell type that stores triacylglycerols (TGs) in cytoplasmic lipid droplets (LDs). We revisit TG metabolism in enterocytes by ex vivo and in vivo coherent anti-Stokes Raman scattering (CARS) imaging of small intestine of mice during dietary fat absorption (DFA). We directly visualized the presence of LDs in enterocytes. We determined lipid amount and quantified LD number and size as a function of intestinal location and time post-lipid challenge via gavage feeding. The LDs were confirmed to be primarily TG by biochemical analysis. Combined CARS and fluorescence imaging indicated that the large LDs were located in the cytoplasm, associated with the tail-interacting protein of 47 kDa. Furthermore, in vivo CARS imaging showed real-time variation in the amount of TG stored in LDs through the process of DFA. Our results highlight a dynamic, cytoplasmic TG pool in enterocytes that may play previously unexpected roles in processes, such as regulating postprandial blood TG concentrations.     

Reduction and coordination of arsenic in Indian mustard

The bioaccumulation of arsenic by plants may provide a means of removing this element from contaminated soils and waters. However, to optimize this process it is important to understand the biological mechanisms involved. Using a combination of techniques, including x-ray absorption spectroscopy, we have established the biochemical fate of arsenic taken up by Indian mustard (Brassica juncea). After arsenate uptake by the roots, possibly via the phosphate transport mechanism, a small fraction is exported to the shoot via the xylem as the oxyanions arsenate and arsenite. Once in the shoot, the arsenic is stored as an As(III)-tris-thiolate complex. The majority of the arsenic remains in the roots as an As(III)-tris-thiolate complex, which is indistinguishable from that found in the shoots and from As(III)-tris-glutathione. The thiolate donors are thus probably either glutathione or phytochelatins. The addition of the dithiol arsenic chelator dimercaptosuccinate to the hydroponic culture medium caused a 5-fold-increased arsenic level in the leaves, although the total arsenic accumulation was only marginally increased. This suggests that the addition of dimercaptosuccinate to arsenic-contaminated soils may provide a way to promote arsenic bioaccumulation in plant shoots, a process that will be essential for the development of an efficient phytoremediation strategy for this element.     

Hoarding by honeybees (Apis mellifera L.)

The food hoarding by groups of fifty bees kept in small cages and provided with sugar syrup was studied. Less food was stored in a new comb than in an old one, whether the old comb had been used for storing food or rearing brood, and there was less in drone than in worker combs. The presence of light, larvae and the odour of honey discouraged storage of syrup, but the presence of a queen encouraged it. The amount stored also varied with the environmental temperature, the age of the bees concerned and with their previous physiological and behavioural experience including food deprivation and length of confinement. Increased food in honeystomachs sometimes compensated for less stored in combs.