Morphological evaluation of MDA-MB-231 human breast cancer cells treated with DMEM extract of Turkish propolis

Purpose: To evaluate the influence of DMEM extract of Turkish propolis (TP) on the morphology of metastatic MDA-MB-231 cells. Methods: The cells were incubated with DMEM extract of TP (collected from Trabzon in Turkey) at a dose of 2.5 mg/mL for 72 h. The effect of DMEM extract on proliferation and cytotoxicity of the cells was determined using 3-[4,5-dimethyltiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and trypan blue exclusion assay. MDA-MB-231 cells incubated with or without extracts were randomly photographed with a camera-coupled inverted microscope. Treated and control MDA-MB-231 cells were classified as monopolar, bipolar or multipolar, and their dimensions measured with an electronic caliper. Results: Although the extract reduced the proliferation of the cells, the effect was not statistically significant (p < 0.05). Moreover, no cytotoxic effect was observed. Field diameters, process length and cell body diameters of the treated cells were increased by DMEM extract treatment in bipolar and multipolar cell types, but these parameters were decreased in monopolar cell type, although insignificantly (p < 0.05). In addition, the process thickness of treated MDA-MB-231 cells increased insignificantly in all cell types (p < 0.05). Conclusion: These findings indicate that DMEM extract of TP at a dose of 2.5 mg/mL morphologically suppresses monopolar MDA-MB-231 cells. Future studies would examine the morphological effects of different concentrations of the propolis extract in anti-proliferation, cytotoxicity and morphological investigations in MDA-MB-231 cells.

Sign-conserving amacrine neurons in the fly's external plexiform layer

Amacrine cells in the external plexiform layer of the fly's lamina have been intracellulary recorded and dye-filled for the first time. The recordings demonstrate that like the lamina's short photoreceptors R1–R6, type 1 lamina amacrine neurons exhibit nonspiking, “sign-conserving” sustained depolarizations in response to illumination. This contrasts with the sign-inverting responses that typify first-order retinotopic relay neurons: monopolar cells L1–L5 and the T1 efferent neuron. The contrast frequency tuning of amacrine neurons is similar to that of photoreceptors and large lamina monopolar cells. Initial observations indicate that lamina amacrine receptive fields are also photoreceptor-like, suggesting either that their inputs originate from a small number of neighboring visual sampling units (VSUs), or that locally generated potentials decay rapidly with displacement. Lamina amacrines also respond to motion, and in one recording these responses were selective for the orientation of moving edges. This functional organization corresponds to the anatomy of amacrine cells, in which postsynaptic inputs from several neighboring photoreceptor endings are linked by a network of very thin distal processes. In this way, each VSU can receive convergent inputs from a surround of amacrine processes. This arrangement is well suited for relaying responses to local intensity fluctuations from neighboring VSUs to a central VSU where amacrines are known to be presynaptic to the dendrites of the T1 efferent. The T1 terminal converges at a deeper level with that of the L2 monopolar cell relaying from the same optic cartridge. Thus, the localized spatial responses and receptor-like temporal response properties of amacrines are consistent with possible roles in lateral inhibition, motion processing, or orientation processing.

Mechanisms for Neural Signal Enhancement in the Blowfly Compound Eye

In the blowfly Calliphora vicina visual signals are enhanced by amplification and antagonism as they pass from the site of phototransduction in the retina to secondorder neurones (LMCs) in the first optic neuropile, the lamina. The mechanisms responsible for amplification and antagonism were investigated, using currentclamp techniques, to examine the conductance mechanisms generating LMC responses. LMCs responded Ohmically to injected current. Voltage-sensitive conductances and feedback mechanisms driven by the potential of a single LMC played a minor role in shaping responses. The LMCs response to an increment in illumination, a transient hyperpolarization, was generated by a large and transient conductance increase with a reversal potential close to the maximum response amplitude (30–40mV below dark resting potential). The depolarization of the C in response to a decrement in light intensity was partially generated by a reduction in direct synaptic input from the photoreceptors. Changes in depolarizing conductances with positive reversal potentials played a secondary role, contributing to large-amplitude responses to dimming or light-off, and to the slow decay of the LMC response to steady illumination. Antagonism, including lateral antagonism, operated principally by shutting down the direct photoreceptor input, presumably by presynaptic regulation. The results of dye injection suggested that the identified large monopolar cell L2 is more strongly affected by lateral antagonism than the similar cells L1 and L3. We conclude that LMCs are essentially passive integrators of a well-regulated direct input from the photoreceptors. This suggests that the intrinsic properties of photoreceptor-LMC synapses and presynaptic interactions are primarily responsible for amplification and antagonism.

Terminations of photoreceptor axons from different regions of the compound eye of the desert ant Cataglyphis bicolor

The morphology of the photoreceptors from different regions of the desert an t’s compound eye is investigated by Golgi-impregnations and anterograde or retrograde haem peptide filling, combined with electron microscopy. A new type of receptor axon is described. This receptor is of the short (svf) type but terminates in the proximal layer of the lamina (epl-C), in contrast to the other short visual fibres, which terminate in the distal layer (epl-A) : Golgi-EM investigations show that this receptor axon belongs to the small photoreceptor R9. The receptor R9 appears to be pre- and postsynaptic to other receptor axons and to second order neurons. In each ommatidium, the axons of the two long photoreceptors (lvf) R1 and R5 (probably uv-receptors) remain paired down to their terminations in the distal layer of the medulla. The regional specialization of the retina (dorsal rim area (dra), dorsal retina (dr) and ventral retina (vr)) is reflected by the morphology of the receptor terminals and the second order neurons. The lamina underlying the dra consists of only one layer, an extended epl-A; in the remainder of the eye, the lamina is trilateral. In the dra all short visual fibres (svf) are equal in length. The extension of the monopolar cell dendrites is restricted to one cartridge only. In the medulla, the terminals of the lvfs deriving from the dra (R1 and R5) have more extensive arborizations than elsewhere in the eye.

The lamina monopolar cells in the optic lobe of the dragonfly sympetrum

The connectivities of five monopolar cells, M I-M V, within the ventral cartridge of the lamina of the dragonfly Sympetrum have been analysed from serial electron microscopy and their morphologies confirmed from Golgi-electron microscopy. The results of synaptic analyses are presented from a single cartridge photographed in its entirety in one series of transverse sections through the complete depth of the lamina and corroborated from shorter series of sections of additional cartridges. Each monopolar cell is defined by and identified from the location of its soma and the characteristic position of its axon in the cartridge cross section. M I and M II are two axial monopolar cells with large-calibre axons, while axons of M III-M V are slender and occupy polar positions, M III and M IV next to M I, M V next to the long visual fibres R 6 and R 7. M I and M II contribute postsynaptically at the triad synapses of all six retinular terminals, M I contributing exclusively at its dendrites, which number about 50 % more than those of M II. The distribution of M I and M II dendrites in general reflects the geometry and extent of synaptic engagement with the surrounding retinular terminals. In addition M II is postsynaptic at synapses of the long visual fibres R 6 and R 7, thus receiving a comprehensive and exclusive receptor input; it is only postsynaptic in the lamina. M I, on the other hand, forms an output back upon certain of its retinular inputs and upon M IV. M III too forms an important output upon M IV and it receives a selective retinular input from R 1 at synapses that are the focus of an unexpected asymmetry within the cartridge. M V, like M III, receives a selective retinular input (from R 7) while M IV receives its retinular input only indirectly, from both M I and M III. M IV and M V, like M II, have no output within the lamina. Finally, all monopolar cells excluding M II receive input from an unidentified cell type or types, called a, an input that for M I and M III is reciprocal. To judge from the diversity of their synaptic configurations, the numbers of their dendrites and probably the numbers of their synapses too, the monopolar cells form a sequence in ascending richness M V -M I. Definite parallels exist between, respectively, M I and M II of Sympetrum and L 2 and L 1 of Musca and Apis and between M III of Sympetrum and L 3 of Apis ,but further homologies are unclear