The cole-moore effect in nodal membrane of the frogRana ridibunda: Evidence for fast and slow potassium channels

Summary The K conductance (g _K) kinetics were studied in voltage-clamped frog nodes (Rana ridibunda) in double-pulse experiments. The Cole-Moore translation forg _K–t curves associated with different initial potentials (E) was only observed with a small percentage of fibers. The absence of the translation was found to be caused by the involvement of an additional, slow,g _K component. This component cannot be attributed to a multiple-state performance of the K channel. It can only be accounted for by a separate, slow K channel, the fast channel being the same as then ⁴ K channel inR. pipiens.The slow K channel is characterized by weaker sensitivity to TEA, smaller density, weaker potential (E) dependence, and somewhat more negativeE range of activation than the fast K channel. According to characteristics of the slow K system, three types of fibers were found. In Type I fibers (most numerous) the slow K channel behaves as ann ⁴ HH channel. In Type II fibers (the second largest group found) the slow K channel obeys the HH kinetics within a certainE range only; beyond this range the exponential decline of the slowg _K component is preceded by anE-dependent delay, its kinetics after the delay being the same as those in Type I fibers. In Type III fibers (rare) the slow K channel is lacking, and it is only in these fibers that the Cole-Moore translation of the measuredg _K–t curves can be observed directly.The physiological role of the fast and slow K channel in amphibian nerves is briefly discussed.     

The identification of an epoxy-hydroxy acid as a product from the incubation of arachidonic acid with washed blood platelets

An epoxy-hydroxy compound, 10-hydroxy-11,12-epoxy-eicosa-5,8,14-trienoic acid, has been identified as a product on incubation of arachidonic acid with washed blood platelets from human, horse, cat, dog and rabbit. Gas chromatographic - mass spectrometric (GC-MS) evidence of structure is discussed.     

Homing behavior of pigeons not disturbed by application of an olfactory stimulus

Summary In a second attempt to repeat recently published experiments that appear to support an hypothesis that olfactory cues play an important role in pigeon navigation, we have conducted 15 experiments in which-pinene in vaseline was applied to the birds' beak and nostrils prior to release, a procedure reported by Benvenutiet al. (1973) to cause a decrement in homing performance. Our results show no consistent difference between the experimental and control birds in any of the three parameters (initial orientation, rapidity of orientation, homing speed) measured by Benvenutiet al. We thank our colleagues Timothy Larkin, Marilyn Yodlowski, and Lindsay Goodloe for their help in conducting the releases. This research was supported by Grant BMS 72-02198-AO2 from the National Science Foundation.     

Synaptic development in the crayfish opener muscle

Nerve terminal regions in walking leg opener muscles of several crayfish of different ages (0 to 245 days after hatching) were examined by means of electron microscopy. This muscle is innervated by two axons (excitatory and inhibitory) and at maturity contains three classes of synapse: excitatory and inhibitory neuromuscular synapses, and inhibitory axo-axonal synapses. The muscle itself is initially a syncytium, which gradually becomes subdivided into distinct “muscle fibers” as the animal matures. Innervation was not found in the opener muscle just before or just after hatching, but was present in restricted locations on the inner side of the muscle within a few days of hatching. As the muscle enlarged and became subdivided, innervation appeared in various other locations. Synaptic contacts were located in young stages soon after hatching, and in later stages. Morphological differences characteristic of excitatory and inhibitory nerve terminals could be found even at the earliest stages of innervation. Both excitatory and inhibitory synapses, but particularly the former, showed evidence of progressive enlargement to a final size within the first two months, and no evidence for further enlargement of existing synapses thereafter. Synaptic maturation also involved the appearance of presynaptic “dense bodies” thought to be regions at which transmitter substance is preferentially released. Nerve terminals at different levels of maturation were observed in opener muscles of young crayfish. Clear evidence for differential maturation of the three types of synapse present in this muscle was obtained. The inhibitory neuromuscular synapses attained their final average size and developed their dense bodies sooner than the excitatory neuromuscular synapses. The inhibitory axo-axonal synapses were the last to appear and to mature.     

Starling Flock Networks Manage Uncertainty in Consensus at Low Cost

Flocks of starlings exhibit a remarkable ability to maintain cohesion as a group in highly uncertain environments and with limited, noisy information. Recent work demonstrated that individual starlings within large flocks respond to a fixed number of nearest neighbors, but until now it was not understood why this number is seven. We analyze robustness to uncertainty of consensus in empirical data from multiple starling flocks and show that the flock interaction networks with six or seven neighbors optimize the trade-off between group cohesion and individual effort. We can distinguish these numbers of neighbors from fewer or greater numbers using our systems-theoretic approach to measuring robustness of interaction networks as a function of the network structure, i.e., who is sensing whom. The metric quantifies the disagreement within the network due to disturbances and noise during consensus behavior and can be evaluated over a parameterized family of hypothesized sensing strategies (here the parameter is number of neighbors). We use this approach to further show that for the range of flocks studied the optimal number of neighbors does not depend on the number of birds within a flock; rather, it depends on the shape, notably the thickness, of the flock. The results suggest that robustness to uncertainty may have been a factor in the evolution of flocking for starlings. More generally, our results elucidate the role of the interaction network on uncertainty management in collective behavior, and motivate the application of our approach to other biological networks.     

Ancient Cytokines,the Role of Astakines as Hematopoietic Growth Factors

Hematopoiesis is the process by which hemocytes mature and subsequently enter the circulation. Vertebrate prokineticins (PKs) are known to take part in this process, as are the invertebrate prokineticin domain proteins, astakines. In Pacifastacus leniusculus, astakine 1 is essential for the release of new hemocytes into the open circulatory system of these animals. In addition to astakine 1, we have now cloned a homologue of astakine 1 with an insert of 13 amino acids, named as astakine 2. Both crustacean astakines lack the N-terminal AVIT motif, which is present in vertebrate PKs, and hence receptor binding differs from that of vertebrate PKs. We have found astakine-like sequences in 19 different invertebrate species, and the sequences show that some motifs are conserved among invertebrate groups. Previously we showed that astakine 1 is directly involved in hematopoiesis, and now we show that astakine 1 and astakine 2 have different roles in hemocyte lineage differentiation. Astakine 1 can stimulate proliferation of hematopoietic tissue (Hpt) cells (precursor of hemocytes) as well as specifically induce differentiation of Hpt cells along the semigranular cell lineage, whereas astakine 2 plays a role in granular cell differentiation. Moreover, we discuss the impact of the putative structures of different astakines in comparison with the vertebrate prokineticins.     

A direct technique for the preparation of chromosomes from early equine embryos

A technique is described for the preparation of banded chromosomes from early equine embryos cultured for less than 10 h in a medium containing bromodeoxyuridine. In addition to standard Giemsa staining and C-banding, chromosomes thus prepared can also be R-banded by either the RBA or the RB-FPG methods. This technique is rapid, repeatable, and limits cell loss, making it ideal for the preparation of early embryos.