Mary Jane Hogue (1883-1962): A pioneer in human brain tissue culture.

The ability to maintain human brain explants in tissue culture was a critical step in the use of these cells for the study of central nervous system disorders. Ross G. Harrison (1870-1959) was the first to successfully maintain frog medullary tissue in culture in 1907, but it took another 38 years before successful culture of human brain tissue was accomplished. One of the pioneers in this achievement was Mary Jane Hogue (1883-1962). Hogue was born into a Quaker family in 1883 in West Chester, Pennsylvania, and received her undergraduate degree from Goucher College in Baltimore, Maryland. Research with the developmental biologist Theodor Boveri (1862-1915) in Würzburg, Germany, resulted in her Ph.D. (1909). Hogue transitioned from studying protozoa to the culture of human brain tissue in the 1940s and 1950s, when she was one of the first to culture cells from human fetal, infant, and adult brain explants. We review Hogue's pioneering contributions to the study of human brain cells in culture, her putative identification of progenitor neuroblast and/or glioblast cells, and her use of the cultures to study the cytopathogenic effects of poliovirus. We also put Hogue's work in perspective by discussing how other women pioneers in tissue culture influenced Hogue and her research.

The Marine Biological Laboratory (Woods Hole) and the scientific advancement of women in the early 20th century: the example of Mary Jane Hogue (1883-1962).

The Marine Biological Laboratory (MBL) in Woods Hole, MA provided opportunities for women to conduct research in the late 19th and early 20th century at a time when many barriers existed to their pursuit of a scientific career. One woman who benefited from the welcoming environment at the MBL was Mary Jane Hogue. Her remarkable career as an experimental biologist spanned over 55 years. Hogue was born into a Quaker family in 1883 and received her undergraduate degree from Goucher College. She went to Germany to obtain an advanced degree, and her research at the University of Würzburg with Theodor Boveri resulted in her Ph.D. (1909). Although her research interests included experimental embryology, and the use of tissue culture to study a variety of cell types, she is considered foremost a protozoologist. Her extraordinary demonstration of chromidia (multiple fission) in the life history of a new species of Flabellula associated with diseased oyster beds is as important as it is ignored. We discuss Hogue's career path and her science to highlight the importance of an informal network of teachers, research advisors, and other women scientists at the MBL all of whom contributed to her success as a woman scientist.

Neuroarchitecture of the arcuate body in the brain of the spider Cupiennius salei (Araneae, Chelicerata) revealed by allatostatin-, proctolin-, and CCAP-immunocytochemistry and its evolutionary implications.

Here we describe the neuronal organization of the arcuate body in the brain of the wandering spider Cupiennius salei. The internal anatomy of this major brain center is analyzed in detail based on allatostatin-, proctolin-, and crustacean cardioactive peptide (CCAP)-immunohistochemistry. Prominent neuronal features are demonstrated in graphic reconstructions. The stainings revealed that the neuroarchitecture of the arcuate body is characterized by several distinct layers some of which comprise nerve terminals that are organized in columnar, palisade-like arrays. The anatomy of the spider's arcuate body exhibits similarities as well as differences when compared to the central complex in the protocerebrum of the Tetraconata. Arguments for and against a possible homology of the arcuate body of the Chelicerata and the central complex of the Tetraconata and their consequences for the understanding of arthropod brain evolution are discussed.

Otoacoustic emissions in bushcricket ears: general characteristics and the influence of the neuroactive insecticide pymetrozine.

The tympanal organ of the bushcricket Mecopoda elongata emits pronounced distortion-product otoacoustic emissions (DPOAEs). Their characteristics are comparable to those measured in other insects, such as locusts and moths, with the 2f1-f2 emission being the most prominent one. Yet the site of their generation is still unclear. The spatial separation between the sound receiving spiracle and the hearing organ in this species allows manipulations of the sensory cells without interfering with the acoustical measurements. We tried to interfere with the DPOAE generation by pharmacologically influencing the tympanal organ using the insecticide pymetrozine. The compound appears to act selectively on scolopidia, i.e., the mechanosensor type characteristically constituting tympanal organs. Pymetrozine solutions were applied as closely as possible to the scolopidia via a cuticle opening in the tibia, distally to the organ. Applications of pymetrozine at concentrations between 10(-3) and 10(-7) M to the tympanal organ led to a pronounced and irreversible decrease of the DPOAE amplitudes.

Johann Flögel (1834-1918) and the birth of comparative insect neuroanatomy and brain nomenclature.

Johann H.L. Flögel (1834-1918) was an amateur scientist and self-taught microscopist in Germany who 130years ago pioneered comparative arthropod neuroanatomy. He was fascinated by innovations in optical instrumentation, and his meticulous studies of the insect supraoesophageal ganglia were the first to use serial sections and photomicrographs to characterize the architecture of circumscribed regions of brain tissue. Flögel recognized the interpretative power resulting from observations across various species, and his comparative study of 1878, in particular, provided a baseline for subsequent workers to evolve a secure nomenclature of insect brain structures. His contributions stand out from contemporary accounts by virtue of their disciplined descriptions and emphasis on identifying comparable elements in different taxa. Here we give a biographical sketch of his life and summarize his remarkable achievements.

Otoacoustic emissions from insect ears: evidence of active hearing?

Sensitive hearing organs often employ nonlinear mechanical sound processing which generates distortion-product otoacoustic emissions (DPOAE). Such emissions are also recordable from tympanal organs of insects. In vertebrates (including humans), otoacoustic emissions are considered by-products of active sound amplification through specialized sensory receptor cells in the inner ear. Force generated by these cells primarily augments the displacement amplitude of the basilar membrane and thus increases auditory sensitivity. As in vertebrates, the emissions from insect ears are based on nonlinear mechanical properties of the sense organ. Apparently, to achieve maximum sensitivity, convergent evolutionary principles have been realized in the micromechanics of these hearing organs-although vertebrates and insects possess quite different types of receptor cells in their ears. Just as in vertebrates, otoacoustic emissions from insects ears are vulnerable and depend on an intact metabolism, but so far in tympanal organs, it is not clear if auditory nonlinearity is achieved by active motility of the sensory neurons or if passive cellular characteristics cause the nonlinear behavior. In the antennal ears of flies and mosquitoes, however, active vibrations of the flagellum have been demonstrated. Our review concentrates on experiments studying the tympanal organs of grasshoppers and moths; we show that their otoacoustic emissions are produced in a frequency-specific way and can be modified by electrical stimulation of the sensory cells. Even the simple ears of notodontid moths produce distinct emissions, although they have just one auditory neuron. At present it is still uncertain, both in vertebrates and in insects, if the nonlinear amplification so essential for sensitive sound processing is primarily due to motility of the somata of specialized sensory cells or to active movement of their (stereo-)cilia. We anticipate that further experiments with the relatively simple ears of insects will help answer these questions.

Evolutionary changes in sensory precursor formation in arthropods: embryonic development of leg sensilla in the spider Cupiennius salei.

We describe here for the first time the development of mechanosensory organs in a chelicerate, the spider Cupiennius salei. It has been shown previously that the number of external sense organs increases with each moult. While stage 1 larvae do not have any external sensory structures, stage 2 larvae show a stereotyped pattern of touch sensitive 'tactile hairs' on their legs. We show that these mechanosensory organs develop during embryogenesis. In contrast to insects, groups of sensory precursors are recruited from the leg epithelium, rather than single sensory organ progenitors. The groups increase by proliferation, and neural cells delaminate from the cluster, which migrate away to occupy a position proximal to the accessory cells of the sense organ. In addition, we describe the development of putative internal sense organs, which do not differentiate until larval stage 2. We show by RNA interference that, similar to Drosophila, proneural genes are responsible for the formation and subtype identity of sensory organs. Furthermore, we demonstrate an additional function for proneural genes in the coordinated invagination and migration of neural cells during sensory organ formation in the spider.

Reticulospinal neurons in anamniotic vertebrates: a celebration of Alberto Stefanelli's contributions to comparative neuroscience.

Over the past 76 years Alberto Stefanelli has successfully used a comparative approach to study the nervous system. His main research focus during that time has been on identifiable reticulospinal neurons including Müller and Mauthner neurons found in anamniotic vertebrates. Born in Venice, Italy in 1908, Professor Stefanelli pursued most of his academic career at the University of Rome, where he retired as Chair of Comparative Anatomy in 1978. His seminal work on the constancy in number and position of giant identifiable reticulospinal neurons in the brains of larval and adult lampreys, and his assertion that only a subset of these neurons were Müller cells, provided the framework in which subsequent authors have refined our understanding of the cellular anatomy, axonal projections, physiology, and function of Müller cells in the control of movement. Stefanelli has also provided the most comprehensive study to date of the Mauthner cell and its axon cap. His description of the differences in axon cap structure among many fishes and amphibians and his use of the "morpho-ecological" approach to determine Mauthner cell function has provided the basis for future studies on the neuronal basis of behavior and its evolution. As Professor Stefanelli approaches his 100th birthday, we celebrate his scientific contributions to comparative neuroscience with a biographical sketch of his life, an overview of his scientific accomplishments, and our view of how his comparative studies continue to contribute to our understanding of the nervous system.

Otoacoustic emissions from insect ears having just one auditory neuron.

Sensitive hearing organs often employ nonlinear mechanical sound processing which produces distortion-product otoacoustic emissions. Such emissions are also recorded from insect tympanal organs. Here we report high frequency distortion-product emissions, evoked by stimulus frequencies up to 95 kHz, from the tympanal organ of a notodontid moth, Ptilodon cucullina, which contains only a single auditory receptor neuron. The 2f1-f2 distortion-product emission reaches sound levels above 40 dB SPL. Most emission growth functions show a prominent notch of 20 dB depth (n = 20 trials), accompanied by an average phase shift of 119 degrees , at stimulus levels between 60 and 70 dB SPL, which separates a low- and a high-level component. The emissions are vulnerable to topical application of ethyl ether which shifts growth functions by about 20 dB towards higher stimulus levels. For the mammalian cochlea, Lukashkin and colleagues have proposed that distinct level-dependent components of nonlinear amplification do not necessarily require interaction of several cellular sources but could be due to a single nonlinear source. In notodontids, such a physiologically vulnerable source could be the single receptor cell. Potential contributions from accessory cells to the nonlinear properties of the scolopidial hearing organ are still unclear.

The generation of DPOAEs in the locust ear is contingent upon the sensory neurons.

Tympanal organs of insects emit distortion-product otoacoustic emissions (DPOAEs) that are indicative of nonlinear ear mechanics. Our study sought (1) to define constraints of DPOAE generation in the ear of Locusta migratoria, and (2) to identify the sensory structures involved. We selectively destroyed the connection between the (peripheral) sensory ganglion and the tympanal attachment points of the "d-cell" dendrites; d-cells are most sensitive to sound frequencies above 12 kHz. This led to a decrease of DPOAEs that were evoked by f (2) frequencies above 15 kHz (decrease of 15-40 dB; mean 28 dB; n = 12 organs). DPOAEs elicited by lower frequencies remained unchanged. Such frequency-specific changes following the exclusion of one scolopidial sub-population suggest that these auditory scolopidia are in fact the source of DPOAEs in insects. Electrical stimulation of the auditory nerve (with short current pulses of 4-10 microA or DC-currents of 0.5 microA) reversibly reduced DPOAEs by as much as 30 dB. We assume that retrograde electrical stimulation primarily affected the neuronal part of the scolopidia. Severing the auditory nerve from the central nervous system (CNS) did not alter the DPOAE amplitudes nor the effects of electrical stimulation.

Julius Bernstein (1839-1917): pioneer neurobiologist and biophysicist.

Julius Bernstein belonged to the Berlin school of "organic physicists" who played a prominent role in creating modern physiology and biophysics during the second half of the nineteenth century. He trained under du Bois-Reymond in Berlin, worked with von Helmholtz in Heidelberg, and finally became Professor of Physiology at the University of Halle. Nowadays his name is primarily associated with two discoveries: (1) The first accurate description of the action potential in 1868. He developed a new instrument, a differential rheotome (= current slicer) that allowed him to resolve the exact time course of electrical activity in nerve and muscle and to measure its conduction velocity. (2) His 'Membrane Theory of Electrical Potentials' in biological cells and tissues. This theory, published by Bernstein in 1902, provided the first plausible physico-chemical model of bioelectric events; its fundamental concepts remain valid to this day. Bernstein pursued an intense and long-range program of research in which he achieved a new level of precision and refinement by formulating quantitative theories supported by exact measurements. The innovative design and application of his electromechanical instruments were milestones in the development of biomedical engineering techniques. His seminal work prepared the ground for hypotheses and experiments on the conduction of the nervous impulse and ultimately the transmission of information in the nervous system. Shortly after his retirement, Bernstein (1912) summarized his electrophysiological work and extended his theoretical concepts in a book Elektrobiologie that became a classic in its field. The Bernstein Centers for Computational Neuroscience recently established at several universities in Germany were named to honor the person and his work.

From stress and strain to spikes: mechanotransduction in spider slit sensilla.

This review focuses on the structure and function of a single mechanoreceptor organ in the cuticle of spiders. Knowledge emerging from the study of this organ promises to yield general principles that can be applied to mechanosensation in a wide range of animal systems. The lyriform slit sense organ on the antero-lateral leg patella of the spider Cupiennius salei is unusual in possessing large sensory neurons, whose cell bodies are close to the sites of sensory transduction, and accessible to intracellular recording during mechanotransduction. This situation, combined with recent technical developments, has made it possible to observe and experiment with all the major stages of mechanosensation. Important findings include the approximate size, number and ionic selectivity of the ion channels responsible for mechanotransduction, the types of voltage-activated ion channels responsible for action potential encoding, and the mechanisms controlling the dynamic properties of transduction and encoding. Most recently, a complex efferent system for peripheral modulation of mechanosensation has been discovered and partially characterized. Much remains to be learned about mechanosensation, but the lyriform slit sense organ system continues to offer important opportunities to advance our understanding of this crucial sense.

Peripheral synaptic contacts at mechanoreceptors in arachnids and crustaceans: morphological and immunocytochemical characteristics.

Two types of sensory organs in crustaceans and arachnids, the various mechanoreceptors of spiders and the crustacean muscle receptor organs (MRO), receive extensive efferent synaptic innervation in the periphery. Although the two sensory systems are quite different-the MRO is a muscle stretch receptor while most spider mechanoreceptors are cuticular sensilla-this innervation exhibits marked similarities. Detailed ultrastructural investigations of the synaptic contacts along the mechanosensitive neurons of a spider slit sense organ reveal four important features, all having remarkable resemblances to the synaptic innervation at the MRO: (1) The mechanosensory neurons are accompanied by several fine fibers of central origin, which are presynaptic upon the mechanoreceptors. Efferent control of sensory function has only recently been confirmed electrophysiologically for the peripheral innervation of spider slit sensilla. (2) Different microcircuit configuration types, identified on the basis of the structural organization of their synapses. (3) Synaptic contacts, not only upon the sensory neurons but also between the efferent fibers themselves. (4) Two identified neurotransmitter candidates, GABA and glutamate. Physiological evidence for GABAergic and glutamatergic transmission is incomplete at spider sensilla. Given that the sensory neurons are quite different in their location and origin, these parallels are most likely convergent. Although their significance is only partially understood, mostly from work on the MRO, the close similarities seem to reflect functional constraints on the organization of efferent pathways in the brain and in the periphery.

Peripheral GABAergic inhibition of spider mechanosensory afferents.

Spider mechanosensory neurons receive an extensive network of efferent synapses onto their sensory dendrites, somata and distal axonal regions. The function of these synapses is unknown. Peripheral synapses are also found on crustacean stretch-receptor neurons but not on mechanosensory afferents of other species, although inhibitory GABAergic synapses are a common feature of centrally located axon terminals. Here we investigated the effects of GABA receptor agonists and antagonists on one group of spider mechanosensory neurons, the slit sense organ VS-3, which are accessible to current- and voltage-clamp recordings. Bath application of GABA activated an inward current that depolarized the membrane and increased the membrane conductance leading to impulse inhibition. VS-3 neuron GABA receptors were activated by muscimol and inhibited by picrotoxin but not bicuculline, and their dose-response relationship had an EC(50) of 103.4 microm, features typical for insect ionotropic GABA receptors. Voltage- and current-clamp analysis confirmed that, while the Na(+) channel inhibition resulting from depolarization can lead to impulse inhibition, the increase in membrane conductance (i.e. 'shunting') completely inhibited impulse propagation. This result argues against previous findings from other preparations that GABA-mediated inhibition is caused by a depolarization that inactivates Na(+) conductance, and it supports those findings that assign this role to membrane shunting. Our results show that GABA can rapidly and selectively inhibit specific mechanoreceptors in the periphery. This type of peripheral inhibition may provide spiders with a mechanism for distinguishing between signals from potential prey, predators or mates, and responding with appropriate behaviour to each signal.

Spiders of the genus Cupiennius Simon 1891 (Araneae, Ctenidae) : I. Range distribution, dwelling plants, and climatic characteristics of the habitats.

Cupiennius is a genus of hunting spiders with seven established species. One of these (C. salei) has been used in laboratory research for many years. Here we report on the geographic distribution of the genus and some characteristics of its habitat. (1) The genus is Central American. Its range is from the state of Veracruz in Mexico in the north to Panama in the south. Five of the seven species are known to occur in the Canal Area, Panama. Sympatry is best documented for C. getazi and C. coccineus and is likely to occur in other species. (2) All known species of Cupiennius are closely associated with particular plants on which they hide during the day and prey, court, and moult at night. The most typical dwelling plant such as a bromeliad or a banana plant is a monocotyledon with mechanically strong and unbranched leaves that provide retreats at their bases. On plants not providing "ready-made" shelters, such as ginger or members of the Araceae, several species of Cupiennius have been observed to build retreats. (3) Average monthly rainfall and temperature data are given for six locations where we have recently observed C. coccineus, C. getazi, C. panamensis, and C. salei. According to measurements taken in the field the microclimate within a typical retreat differs considerably from the external environment: during the day the retreat space shows lower aver-age water evaporation rates and higher relative air humidity.

Spiders of the genus Cupiennius Simon 1891 (Araneae, Ctenidae) : II. On the vibratory environment of a wandering spider.

Cupiennius salei (Ctenidae) is a tropical wandering spider which lives in close association with a particular type of plant (see companion paper). These plants are the channels through which the spiders receive and emit various types of vibrations. We measured the vibrations the spiders are typically exposed to when they sit on their dwelling plants (banana plant, bromeliad) in their natural biotope in Central America. In addition a laboratory analysis was carried out to get an approximate idea of the complex vibration-propagating properties of the dwelling plants, taking a banana plant as an example. (1) Types of vibrations (Figs. 1-4). Despite variability in detail there are characteristic differences in spectral composition between the vibrations of various abiotic and biotic origins: (a) Vibrations due to wind are very low frequency phenomena. Their frequency spectra are conspicuously narrow with prominent peaks close to or, more often, below 10 Hz. Vibrations due to raindrops show maximal acceleration values at ca. 1000 Hz. Their frequency band at-20 dB extends up to ca. 250 Hz where-as that of the vibrations due to wind extends to only ca. 50 Hz. (b) The frequency spectra of prey vibrations such as those generated by a running cockroach are typically broad-banded and contain high frequencies; they have largest peaks mostly between ca. 400 and 900 Hz. Their-20 dB frequency bands usually extend from a few Hz to ca. 900 Hz. Some potential prey animals such as grass-hoppers seem to be vibrocryptic; they walk by the spider as if unnoticed. Their "cautious" gait leads to only weak vibrations at very low frequencies resembling the background noise due to wind. Courtship signals are composed maily of low frequencies, intermediate between background noise and prey vibrations (male: prominent peaks at ca. 75 Hz and ca. 115 Hz; female: dominant frequencies between ca. 20 Hz and ca. 50 Hz). The male signal is composed of "syllables" and differs from all other vibrations studied here by being temporally highly ordered. A comparison with previous electrophysiological studies suggests that the high pass characteristics of the vibration receptors enhance the signal-to-(abiotic)-noise ratio and that the vibration-sensitive interneurons so far examined and found to have band pass characteristics are tuned to the frequencies found in the vibrations of biotic origin. (2) Signal propagation (Fig. 5). In terms of frequency-dependent attenuation of vibrations the banana plant is well suited for transmitting the above signals. Average attenuation values are ca. 0.35 dB/cm. Together with known data on vibration receptor sensitivity this explains the range of courtship signals of more than 1 m observed in behavioral studies. Attenuation in the plant is neither a monotonic function of frequency nor of distance from the signal source.