Changes in the Dendrite Morphology of Mauthner Neurons in Goldfish under the Conditions of Monocular Deprivation and Sensory Stimulation

Biophysics - Abstract—The effects of sensory stimulation on the model of paired Mauthner neurons of monocularly deprived goldfish have been studied by light- and electron microscopy....     

Asymmetry of Motor Behavior of the Goldfish in a Narrow Channel

We studied swimming of goldfish fries about 3 cm long in a narrow channel by calculating the numbers of spontaneous turns on different sides. The ratio of fishes preferring to turn to the right vs to the left was 1.5:1.0, respectively; two-thirds of the fishes demonstrated an ambilateral behavior. Experiments with compulsory 10-min-long rotation of the fishes (clockwise around the longitudinal body axis for fishes preferring right-side turns and anticlockwise for fishes preferring left-side turns) showed that the behavioral asymmetry smoothed somewhat after such a procedure, and a greater number of the fishes became ambilateral in their preference to turn to one side or another. After a one- or two-day-long test, the initial asymmetry of motor behavior completely recovered. Compulsory rotation of similar fishes in the opposite direction exerted no influence on the asymmetry in the choice of the turning direction. Adaptation-induced training of the fishes (using fatiguing long-lasting vestibular stimulation) resulted in some smoothing of motor asymmetry but did not change its general pattern. Thus, our findings allow us to believe that a noticeable proportion of the goldfish individuals (similarly to other animals and humans) is characterized by an innate asymmetry of the motor function with a clear preference for either right- or left-side turnings. These relations can be smoothed under experimental influences but are recovered later on, i.e., they are stable and are not fundamentally transformed. We assume that the asymmetry of motor behavior of fishes in a narrow channel can be an adequate pre-requisite for further examination of the asymmetry of the brain and motor centers controlling changes in locomotion (body turnings)Neirofiziologiya/Neurophysiology, Vol. 37, No. 1, pp. 52–60, January–February, 2005.     

Unilateral Lesion of Dopamine Neurons Induces Grooming Asymmetry in the Mouse

Grooming behaviour is the most common innate behaviour in animals. In rodents, it consists of sequences of movements organized in four phases, executed symmetrically on both sides of the animal and creating a syntactic chain of behavioural events. The grooming syntax can be altered by stress and novelty, as well as by several mutations and brain lesions. Grooming behaviour is known to be affected by alterations of the dopamine system, including dopamine receptor modulation, dopamine alteration in genetically modified animals, and after brain lesion. While a lot is known about the initiation and syntactic modifications of this refined sequence of movements, effects of unilateral lesion of dopamine neurons are unclear particularly regarding the symmetry of syntactic chains. In the present work we studied grooming in mice unilaterally lesioned in the medial forebrain bundle by 6-hydroxydopamine. We found a reduction in completion of grooming bouts, associated with reduction in number of transitions between grooming phases. The data also revealed the development of asymmetry in grooming behaviour, with reduced tendency to groom the contralateral side to the lesion. Symmetry was recovered following treatment with L-DOPA. Thus, the present work shows that unilateral lesion of dopamine neurons reduces self-grooming behaviour by affecting duration and numbers of events. It produces premature discontinuation of grooming chains but the sequence syntax remains correct. This deficient grooming could be considered as an intrinsic symptom of Parkinson’s disease in animal models and could present some similarities with abnormalities of motor movement sequencing seen in patients. Our study also suggests grooming analysis as an additional method to screen parkinsonism in animal models.     

Ultrastructural Changes in the Mixed Synapses of Mauthner Neurons Related to Long-Term Potentiation and Natural Modification of the Motor Function

We examined changes in the ultrastructure of afferent mixed synapses on the membrane of Mauthner neurons (M cells) of the goldfish, which were related to two functional states, long-term potentiation (LTP) of the electrotonic response (a model form of the memory trace) and adaptation (resistivity to fatigue resulting from long-lasting motor training and considered a natural form of the memory trace manifested on the neuronal level). LTP was induced in medullary slices using high-frequency electrical stimulation of the afferent input. Adaptation was produced using natural vestibular stimulation (everyday motor training, which modified motor behavior of the fish and function of the M cell). It was supposed that if the LTP phenomenon is involved in the formation of natural memory, both the adaptation and the LTP states should be accompanied by similar specific structural modifications. Indeed, it was found that in both cases the number of fibrillar bridges in the gaps of desmosome-like contacts (DLC) in the mixed synapses on the M cell surface demonstrated an about twofold increase. These bridges are known to include actin filaments, which function as conductors of cationic signals; thus, the LTP-related increase in the density of bridges corresponds to increased efficacy of electrotonic coupling via mixed synapses. Such a structural correlate of LTP, which probably has the same functional significance in mixed synapses of the adapted M cells, allows us to suppose that LTP is a natural property of the nervous system. The LTP-type intensification of the relay function of mixed synapses, which corresponds to adaptation, is probably a compensatory rearrangement allowing M cells to maintain some balance of the synaptic influences and, at the same time, to remain in a stable and plastic state; this is necessary for stable functioning under changing environmental conditions.     

Reduced Responsiveness to Long-Term Monocular Deprivation of Parvalbumin Neurons Assessed by c-Fos Staining in Rat Visual Cortex

Background

It is generally assumed that visual cortical cells homogeneously shift their ocular dominance (OD) in response to monocular deprivation (MD), however little experimental evidence directly supports this notion. By using immunohistochemistry for the activity-dependent markers c-Fos and Arc, coupled with staining for markers of inhibitory cortical sub-populations, we studied whether long-term MD initiated at P21 differentially affects visual response of inhibitory neurons in rat binocular primary visual cortex.

Methodology/Principal Findings

The inhibitory markers GAD67, parvalbumin (PV), calbindin (CB) and calretinin (CR) were used. Visually activated Arc did not colocalize with PV and was discarded from further studies. MD decreased visually induced c-Fos activation in GAD67 and CR positive neurons. The CB population responded to MD with a decrease of CB expression, while PV cells did not show any effect of MD on c-Fos expression. The persistence of c-Fos expression induced by deprived eye stimulation in PV cells is not likely to be due to a particularly low threshold for activity-dependent c-Fos induction. Indeed, c-Fos induction by increasing concentrations of the GABAA antagonist picrotoxin in visual cortical slices was similar between PV cells and the other cortical neurons.

Conclusion

These data indicate that PV cells are particularly refractory to MD, suggesting that different cortical subpopulation may show different response to MD.     

Changes in Toxicity and Mobility Resulting from Bioremediation Processes

Bioremediation is a commonly used process for the remediation of soils and sludges containing hydrocarbon compounds. The extent of chemical concentration reduction that occurs in bioremediation processes and the concentration of residual chemicals varies widely for different soils and sludges and for different processes. Along with changes in chemical concentration, measures of toxicity and chemical mobility are important information as site remediation decisions are increasingly being made within a risk-based corrective action framework.

This review article presents illustrative data from studies that evaluated the effectiveness of bioremediation processes and that contained information about changes in chemical mobility and soil or sludge toxicity. The weight-of-evidence data presented indicated that, as part of the bioremediation process, there is a reduction of the apparent toxicity of the soils and sludges that were treated. In addition, remaining chemical constituents generally were less mobile. The patterns were consistent for both laboratory and field-scale bioremediation studies.     

Excitability Changes of the Mauthner Cell during Collateral Inhibition

Excitability changes during collateral inhibition of the goldfish Mauthner cell (M cell) were measured directly by stimulating the cell with current pulses applied through an intracellular electrode. Excitability was suppressed during the extrinsic hyperpolarizing potential (EHP) as well as during the collateral IPSP. The inhibitory effect of the EHP was shown to be comparable in intensity to the effect of the IPSP. Excitability changes in the M cell during collateral IPSP depended on changes in the membrane conductance as well as in the membrane potential. Some simple equations are advanced which describe the excitability change during the IPSP in terms of changes in membrane potential and conductance. It was also found that invasion of antidromic impulses into the M cell was suppressed during the EHP, but not during the collateral IPSP. Conductance increase during the IPSP did not interfere with the invasion of antidromic impulses.     

Visual Pigments of Goldfish Cones : Spectral Properties and Dichroism

Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene₂ is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm^–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm^–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra.     

Sleep Deprivation Impairs Object-Selective Attention: A View from the Ventral Visual Cortex

Background

Most prior studies on selective attention in the setting of total sleep deprivation (SD) have focused on behavior or activation within fronto-parietal cognitive control areas. Here, we evaluated the effects of SD on the top-down biasing of activation of ventral visual cortex and on functional connectivity between cognitive control and other brain regions.

Methodology/Principal Findings

Twenty-three healthy young adult volunteers underwent fMRI after a normal night of sleep (RW) and after sleep deprivation in a counterbalanced manner while performing a selective attention task. During this task, pictures of houses or faces were randomly interleaved among scrambled images. Across different blocks, volunteers responded to house but not face pictures, face but not house pictures, or passively viewed pictures without responding. The appearance of task-relevant pictures was unpredictable in this paradigm. SD resulted in less accurate detection of target pictures without affecting the mean false alarm rate or response time. In addition to a reduction of fronto-parietal activation, attending to houses strongly modulated parahippocampal place area (PPA) activation during RW, but this attention-driven biasing of PPA activation was abolished following SD. Additionally, SD resulted in a significant decrement in functional connectivity between the PPA and two cognitive control areas, the left intraparietal sulcus and the left inferior frontal lobe.

Conclusions/Significance

SD impairs selective attention as evidenced by reduced selectivity in PPA activation. Further, reduction in fronto-parietal and ventral visual task-related activation suggests that it also affects sustained attention. Reductions in functional connectivity may be an important additional imaging parameter to consider in characterizing the effects of sleep deprivation on cognition.     

Symmetry and Asymmetry in the Motor Apparatus of the Limbs of Primates

The problem of the nature and mechanism of functional asymmetry in the human motor system has focused attention on the question of the characteristics of the motor apparatus of the limbs of primates.     

Proteomic Changes Resulting from Gene Copy Number Variations in Cancer Cells

Along the transformation process, cells accumulate DNA aberrations, including mutations, translocations, amplifications, and deletions. Despite numerous studies, the overall effects of amplifications and deletions on the end point of gene expression—the level of proteins—is generally unknown. Here we use large-scale and high-resolution proteomics combined with gene copy number analysis to investigate in a global manner to what extent these genomic changes have a proteomic output and therefore the ability to affect cellular transformation. We accurately measure expression levels of 6,735 proteins and directly compare them to the gene copy number. We find that the average effect of these alterations on the protein expression is only a few percent. Nevertheless, by using a novel algorithm, we find the combined impact that many of these regional chromosomal aberrations have at the protein level. We show that proteins encoded by amplified oncogenes are often overexpressed, while adjacent amplified genes, which presumably do not promote growth and survival, are attenuated. Furthermore, regulation of biological processes and molecular complexes is independent of general copy number changes. By connecting the primary genome alteration to their proteomic consequences, this approach helps to interpret the data from large-scale cancer genomics efforts.     

Choline Acetyltransferase Activities in Single Motor Neurons from Vertebrate Spinal Cords

Single cell bodies of spinal motor neurons were isolated from freeze-dried sections of fresh spinal cords from six species of vertebrates. Single human neurons were also isolated from the spinal cords of three autopsy cases without neurological diseases. Choline acetyltransferase activity of these single neurons was determined by measuring acetyl-CoA formation from CoASH and acetylcholine by use of the enzymatic amplification reactions, CoA and NADP cyclings. The enzyme activity was unevenly distributed in the cytosol of spinal motor neurons of all species, but not measurable in rabbit dorsal root ganglion cells. The specific activity on a dry weight basis varied widely among the individual neurons from the species studied. The average activity was highest with rat neurons and lowest with yellowtail neurons. The neurons from cold-blooded animals (bullfrog and yellowtail) had about one-tenth the activity compared with the warm-blooded animals (cat, rabbit, rat, and hen). Human neurons, obtained under different morbid and post-mortem conditions with three autopsy cases, had very low activities corresponding to those of cold-blooded animals. Since the choline acetyltransferase activity lost from mouse brain after 11 h at 38 degrees C was 50%, the activity in human neurons was believed to actually be low in vivo.     

Quantitative Changes in the Structure of The Visual Analyzer Due To Functional Deafferentation

Among the large number of studies of the influence of functional activity on structural elements of the visual analyzer, the study of the peripheral part of the analyzer — the retina — has an important place. With the help of histological and histochemical methods, different authors have established correlates between functional and metabolic shifts in neurons of this part (Brodskiy, 4; Brattgärd, 9; de Robertis, 23).     

Neurochemical Changes in Cerebellum of Goldfish Exposed to Various Temperatures

Acclimation of goldfish at 35°C increased the cerebellar content of aspartate, glutamate, and taurine and [³H]glutamate uptake. Acclimation at 4°C increased the levels of glutamine, serine, and alanine and glutamine synthetase (GS) activity. Adenosine content increased in cerebellum of fish acclimated to warm temperature. K⁺-evoked release of endogenous and exogenous glutamate from cerebellar slices increased in fish acclimated at 35°C compared to 4°C. The basal level of cyclic adenosine 3:5-monophosphate (cAMP) in perfused cerebellar slices in fish acclimated at 35°C was much higher than in fish acclimated at 5° and 22°C. It is concluded that variations of environmental temperature produces large neurochemical changes in goldfish cerebellum.