Serotonin-like immunoreactivity in the optic lobes of three insect species

The cellular localization of 5-HT in the optic lobes of three insect species was assayed with the use of antibodies raised against 5-HT. In Schistocerca, Periplaneta, and Calliphora all neuropil regions of the optic lobe, the lamina, medulla and lobula, contain 5-HT-immunoreactive varicose fibres in different patterns, like columns and layers. Such fibres also connect the lobula to neuropil in the lateral protocerebrum. In Calliphora also 5-HT-positive fibres of the medulla and lobula plate have projections to the lateral protocerebrum, whereas the origin of the lamina fibres is not certain. In all species the processes displaying 5-HT-like immunoreactivity appear to be derived from a relatively small number of cell bodies, each neuron thus having processes over a large volume of the neuropil of the optic lobe in different layers.     

Dynamics of the cytoskeleton in Amoeba proteus

Fluorescein-labeled muscle actin was microinjected into Amoeba proteus and followed during intracellular redistribution by means of the image-intensification technique. The fully polymerization-competent protein becomes part of the endogenous actomyosin system undergoing dynamic changes over time periods of several hours. Single-frame analysis of long-term sequences enabled the direct demonstration of both the contractile activities and morphological transformations of microfilaments in normally locomoting, immobilized and phagocytozing specimens. In normally locomoting cells the filament layer undergoes continuous changes in spatial distribution depending on the actual pattern of cytoplasmic streaming and cell shape. The highest degree of differentiation is always maintained in the intermediate region between the front and the uroid, thus indicating this segment of the cortex to be the most important site in generating motive force for pseudopodium formation and ameboid movement. In immobilized cells contracted by the application of ruthenium red or relaxed by different anesthetics, the filament layer forms a continuous thick sheath beneath the cell surface or becomes completely disintegrated. In phagocytozing cells the local polymerization of actin at the tip of pseudopodia forming the food-cup and around the nascent phagosome points to a significant participation of the actomyosin system in the process of capturing and constricting prey organisms. Although our results provide clear evidence for the overall importance of motive force generation according to the hydraulic pressure theory, some motile phenomena exist in Amoeba proteus that cannot exclusively be explained by this mechanism.     

Lateral Transport of Ions into the Xylem of Corn Roots: II. Evaluation of a Stelar Pump

When an excised corn (Zea mays) root pretreated with chloride was exposed for 10 minutes to pulse labeling with ³⁰Cl and then transferred to unlabeled chloride, the activity in the xylem exudate reached a maximum about 4 minutes after pulse labeling was discontinued and then declined sharply. The rate at which labeled chloride was transported across the root into the xylem and basipetally therein was on the order of 75 to 250 centimeters per hour. Consequently, symplasmic movement of chloride in corn roots is fast and may not be rate-limiting in transfer from the root surface to the xylem. Experiments on pulse labeling with ²²Na gave similar results. A large fraction of the absorbed ²²Na was not translocated into the exudate but was tightly sequestered in a cell compartment, probably the vacuole.     

Cation permeability induced by spermine and polybrene in rat liver mitochondria

The effect of the polybasic substances Polybrene and spermine on the passive and active transport of monovalent cations in mitochondria was studied. These agents were found to stimulate the low amplitude swelling of mitochondria. Volume oscillations were induced by addition of substrate in the presence of spermine. In conditions where weak oscillations were obtained without these substances, oscillations were stimulated and their frequencies increased in the presence of Polybrene and spermine. Their effects were maximal with 100–300 moles spermine per litre and 3–5 mg Polybrene per litre. These results are discussed in relation to an interaction of the agents studied with membrane negative charges which may be important regulators of ion transport.     

Kinetics of gametogenesis

Cell and Tissue Research - In the rat (Wistar-WU) sexual differentiation of the gonads occurs between days 14 and 15 post conception (p.c.). At this time the oogonia and their parallel population...     

Polyamine als Stimulatoren von Genaktivitäten Eine autoradiographische Studie an Riesenchromosomen von Chironomus thummi

Zusammenfassung Inaktive Riesenchromosomen der Speicheldrüsen ausgewachsener Chironomus thummi-Larven zeigten nach 60 min Inkubation mit 0,05 N Putrescin-, Spermidin-oder Spermin-Lösung erneute Syntheseaktivitäten, die sich im Einbau von radioaktiv markiertem Uridin autoradiographisch zu erkennen geben. Diese Beobachtung wird im Zusammenhang mit der bekannten genaktivierenden Wirkung von Mg⁺⁺ diskutiert. Auf der Basis zahlreicher biochemisch analoger Wirkungen von Polyaminen und Mg⁺⁺ wird ein ursprünglich für die genaktivierende Wirkung von Mg⁺⁺ postuliertes Modell auf Polyamine übertragen.

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Stimulation of gene activities by polyamines an autoradiographic study with giant chromosomes of Chironomus thummi

Summary Inactive salivary gland giant chromosomes of full grown Chironomus thummi larvae showed after 60 min of incubation in 0.05 N putrescine, spermidine or spermine solutions autoradiographically demonstrable incorporation of radioactiv labelled uridine caused by a reactivation of RNA synthesis. This observations is discussed in relation to the known gene activating effect of Mg⁺⁺, and, since polyamines and Mg⁺⁺ have numerous effects in common, it is suggested that polyamines affect gene activity in a way similar to Mg⁺⁺.

     

Observations on freeze-fractured membranes of a Trypanosome

Pure preparations of Trypanosoma brucei, free from plasma and cellular components were isolated from rat blood, and concentrated into loose pellets by low-speed centrifugation. Pellets were either processed for thin sectioning as a control for general morphology, or glycerol-treated after glutaraldehyde fixation for preparation of freeze-fracture replicas. Concentration of cells of 50,000–100,000/mm² of sectioned or fractured surface facilitated identification of fracture faces of the cell body, invaginated flagellar pocket and flagellum. Particle distribution and A and B faces of these regions of the cell are described. A collar of B face particles occurs around the neck of the flagellar pocket, possibly associated with a junction controlling ingress of ingested materials to coated vesicles formed along the membrane defining the pocket. A and B faces of the flagellum and adjoining surface of the cell body have shown that the only intra-membrane specialization corresponding to the miniature ‘maculae adherentes’ described previously in thin sections is probably an uninterrupted series of small clusters (3–6) of 80 Å particles on the A face of the flagellar membrane. It is proposed that these arrays represent attachment points for strands linking the axoneme and paraxial rod to the flagellar surface, and are not directly concerned with the physical adhesion of the flagellum to the cell body surface—a linkage that appears to be established within the extracellular gap between these apposed surfaces of the cell. The potential use of freeze-etching in further study of the external antigens of the infective cell is discussed.     

An uncommon inotropically active peptide from dog blood plasma

An octapeptide possessing inotropic activity has been isolated from heparinised dog blood plasma. It was found to be composed of seven isoleucine and one glycine residues and an as yet unidentified compound (X). The aminoacid sequence of its peptide chain was elucidated as iLeu. iLeu. iLeu, iLeu. Gly. iLeu. iLeu. The effect of this peculiar peptide compound on the dog heart papillary muscle was found to parallel that of adrenaline calculated on a Mole/Mole basis. The activity of the peptide compound was destroyed by mineral acid hydrolysis.