Spectral sensitivity of the feedback signal from horizontal cells to cones in goldfish retina

OBJECTIVE: To review the principles and practice of the use of conscious sedation for IVF. DESIGN: The pertinent literature was reviewed and recommendations are provided. RESULT(S): Conscious sedation appears to be the most commonly used method of pain relief for transvaginal retrieval of oocytes. Conscious sedation does not require the presence of an anesthesiologist and can be done in freestanding clinics. Agents commonly used include opioids in combination with benzodiazepines. This combination minimizes pain, decreases anxiety, and provides sedation and some amnesia. Adjuvants such as promethazine and hydroxyzine can also be used but often are not needed. Conscious sedation is well tolerated by patients and does not require highly specialized equipment. However, there are specific safeguards that should be followed. Only a few toxicity studies have been performed, but they are reassuring because they have not found significant effects on fertilization or cleavage. CONCLUSION(S): Conscious sedation appears to be a safe and cost-effective method of providing analgesia and anesthesia for transvaginal retrieval of oocytes.     

Observing response in goldfish (Carassius auratus).

In three experiments we established that goldfish make observing responses. In Experiment 1 fish were rewarded according to a mixed schedule of reinforcement with variable-interval (VI) and extinction (EXT) segments alternating randomly, each in the presence of the same exteroceptive stimulus. By striking a second target the fish in one group could produce a stimulus associated with food (S+). Fish in a second group could produce a stimulus associated with extinction (S–). Although few observing responses were made, fish apparently found aversive the S–. In Experiment 2 fish could respond on a multiple schedule of reinforcement with VI and EXT segments alternating randomly, each in the presence of a different exteroceptive stimulus or on a mixed schedule. Fish preferred the multiple side during VI segments but not during EXT segments until the predictive value of S+ and S– was reduced. In Experiment 3 fish were required to respond to produce S+ and S–. Again, fish preferred the multiple side during VI segments only. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiology of primary saccular afferents of goldfish: implications for Mauthner cell response

Mauthner cells receive neurally coded information from the otolith organs in fishes, and it is most likely that initiation and directional characteristics of the C-start response depend on this input. In the goldfish, saccular afferents are sensitive to sound pressure (< -30 dB re: 1 dyne cm-2) in the most sensitive frequency range (200 to 800 Hz). This input arises from volume fluctuations of the swimbladder in response to the sound pressure waveform and is thus nondirectional. Primary afferents of the saccule, lagena, and utricle of the goldfish also respond with great sensitivity to acoustic particle motion (< 1 nanometer between 100 and 200 Hz). This input arises from the acceleration of the fish in a sound field and is inherently directional. Saccular afferents can be divided into two groups based on their tuning: one group is tuned at about 250 Hz, and the other tuned between 400 Hz and 1 kHz. All otolithic primary afferents phaselock to sinusoids throughout the frequency range of hearing (up to about 2 kHz). Based on physiological and behavioral studies on Mauthner cells, it appears that highly correlated binaural input to the M-cell, from the sacculi responding to sound pressure, may be required for a decision to respond but that the direction of the response is extracted from small deviations from a perfect interaural correlation arising from the directional response of otolith organs to acoustic particle motion.     

The response of primary horizontal semicircular canal neurons in the rat and guinea pig to angular acceleration

In rats and guinea pigs, primary afferent neurons from the horizontal semicircular canal were divided into two categories, regular and irregular, on the basis of the regularity of their resting activity. Regular neurons tend to have higher average resting rates than irregular neurons and in response to a constant angular acceleration stimulus of 16.7 deg/s2 regular neurons tended to have lower sensitivity and longer time constants than irregular cells. Some irregular neurons are more sensitive to incremental accelerations than to decremental accelerations of the same magnitude, whereas regular neurons tend to show symmetrical sensitivity. In response to sinusoidal angular acceleration stimuli (fixed frequencies) in the range 0.01-1.5 Hz, cells which fired regularly at rest tended to have smaller gain and longer phase lag re acceleration at most frequencies than irregular cells. Transfer functions were obtained for averaged data for regular and irregular neurons separately in both species. In both species there is evidence of systematic variation between neurons within each category, and this systematic variation is obscured by averaging across neurons.     

Volume transmission of dopamine may modulate light-adaptive plasticity of horizontal cell dendrites in the recovery phase following dopamine depletion in goldfish retina

We investigated the recovery of light-adaptive spinule formation following dopamine depletion with intraocular injection of 6-hydroxydopamine (6-OHDA) and subsequent neogeneration of dopamine interplexiform cells (DA-IPC) at the marginal zone. DA-IPCs were gone by 2 weeks postinjection and appeared at the marginal zone by 6 weeks postinjection, at which time DA-IPC neurites grew toward the central retina, reaching within 0.5 mm of the central retina by 1 year. Retinas from day time, light-adapted fish at 2 weeks, 4 weeks, 3 months, and 1 year postinjection with 6-OHDA were processed for pre-embedding tyrosine hydroxylase immunoreactivity (TOH-IR) and compared to sham-injected and control retinas at the electron-microscopical (EM) level. Only 6-OHDA fish that tilted markedly toward the injected eye were used for these experiments. The tilt mimics the dorsal light reaction, indicating a 2-2.5 log unit increase in the photopic sensitivity of the 6-OHDA eye. Spinule formation was reduced by about 60% in the 2- and 4-week 6-OHDA retinas, but returned to control levels throughout the entire retina of 3-month and 1 year 6-OHDA retinas even though the central region of these retinas contained no detectable TOH-IR. Intraocular injection with 10 microM SCH 23390 (a D1 antagonist) reduced light-adaptive spinule formation by 50% both in control eyes as well as those eyes that were 3 months post 6-OHDA injected. The full return of spinule formation with only partial reinnervation of the retina with DA-IPC processes and their subsequent inhibition by SCH 23390 indicates that dopamine diffused large distances within the retina to regulate this synaptic plasticity (i.e. displayed volume transmission). Also, since all 6-OHDA injected fish displayed an increased photopic sensitivity in the injected eye when sacrificed, we suggest that horizontal cell spinules are not required for photopic luminosity coding in the outer retina.     

The influence of linear acceleration on optokinetic nystagmus in human subjects

The influence of linear acceleration on optokinetic nystagmus (OKN) was studied in human subjects. Linear acceleration was applied to the subjects by means of the parallel swing and also by the transfer of the subjects in one direction, either right or left. The cortical form of OKN increased the frequency, amplitude, and eye speed of the slow phase. Of the three, the increase in eye speed was the most pronounced. The subcortical form of OKN was not only increased but was also disturbed by the linear acceleration. When the compensatory eye movement with linear acceleration and the slow phase of OKN were in the same direction, the nystagmus increased remarkably. Contrarily, when the two directions were opposed to each other, nystagmus was inhibited. These results proved that the otolithic organs are not only able to promote but also to inhibit visual function.     

The zebrafish brain: a neuroanatomical comparison with the goldfish

The zebrafish Danio rerio is an important model system for genetic and developmental studies of the vertebrate central nervous system. Considerable knowledge concerning the embryonic development of the central nervous system of the zebrafish has accumulated in recent years. However, there is an apparent lack of information on the organization of the adult zebrafish brain. We have therefore recently studied in detail the neuroanatomy of the adult zebrafish. Here we compare the brains of the zebrafish and of the closely related and neurobiologically well-investigated goldfish, Carassius auratus. Two sensory systems, the visual and the gustatory systems, were identified as differing on the gross morphological and histological levels in the two species. The goldfish shows the simple (evolutionarily reduced) pattern of pretectal organization, and its gustatory system is massively enlarged. The pretectum of the zebrafish conforms to this simplified visual pretectal pattern, although the retention of some ancestral pretectal characters indicates a lesser degree of reduction of the visual system compared to the goldfish. The gustatory system shows many similarities with the evolutionarily derived and functionally specialized gustatory system of the goldfish. However, some peripheral and central gustatory characters are missing in the zebrafish, indicating a less specialized gustatory system.     

The ultrastructure of Mauthner's neurons in the surviving medulla oblongata of goldfish

Ultrastructure of Mauthner neurons (MN) was studied in fragments of myelencephalon incubated for 0.5-1.5 hours obtained from immature gold fish. Incubation terms increase along with destruction extent and reorganization of cytoplasmic organelles and nucleus with structure of MN afferent synaptic apparatus less disturbed. Specialized synaptic contacts-active zones, cleft contacts and desmosome-like structure are well retained. The data obtained indicate MN viability during the incubation terms studied, which allows to use surviving grafts with MN as a model for studying ultrastructural bases of certain functional changes of neurons and other neurobiological problems.     

Operant and Pavlovian control of a defensive shuttle response in goldfish (Carassius auratus).

Found that when a visual signal preceded electric shock, goldfish acquired shuttle responses both when a response avoided the shock (operant contingency) and when shock was not avoidable (Pavlovian contingency). Asymptotic levels of responding were significantly higher when shock could be avoided, but were still substantial when shock was not avoidable. Response termination of the signal had little effect on performance. A control experiment showed that responding resulted from the signal-shock contingency and not from nonassociative factors. A search within the Pavlovian contingency for an UCR similar in form to the CR was inconclusive. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Procedure for estimating the correlation dimension of optokinetic nystagmus signals

In this study, optokinetic nystagmus (OKN) is hypothesized to be controlled by a low-dimensional deterministic and possibly chaotic generator. A procedure for quantifying the presumably low-dimensional structure of the OKN signal, based on the Singular Spectrum Approach and the Grassberger--Procaccia algorithm for estimating the correlation dimension, v, is described. The procedure developed showed robustness against noise. Applying this method to OKN signals from 10 healthy subjects and 10 patients suffering from vertigo showed a statistically significant lower mean v value for the patients.     

Incentive shifts in the goldfish.

Trained 157 goldfish with a large or small magnitude of reward in a straight-alley runway. After 20 days of training with a given reward magnitude, 1/2 of the Ss in each group were shifted to the other magnitude of reward. Ss rapidly shifted swimming speeds when reward magnitudes were reversed. No contrast effects were observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spectral sensitivity of the goldfish Torus longitudinalis

We measured the photopic spectral sensitivity of multiunit activity in the torus longitudinalis and optic tectum of goldfish. Since negative contrast stimuli are most effective for exciting torus longitudinalis, spiking activity was evoked by the shadow of a disc moving through a monochromatic light beam projected upon a screen. The amount of activity evoked in torus longitudinalis generally increased with the monochromatic stimulus radiance at the same rate for all wavelengths, indicating a univariant response. Spiking activity in tectum, however, increased at different rates across the spectrum, indicating color-dependent responses. The action spectra for torus longitudinalis were all similar and relatively flat as expected of a homogeneous, broad-band luminance processing system, and about 1 log unit more sensitive than the tectal action spectra. The latter generally displayed sharp peaks and dips in sensitivity indicative of opponent processing.     

Effect of tensilon on the behavior of optokinetic nystagmus in myasthenia

In 14 myasthenics tensilon test was performed together with electronystagmographic recording of optokinetic nystagmus. The mean amplitude of deflections and the mean frequency of nystagmus were calculated before and after intravenous administration of tensilon 10 mg. The results were compared with those obtained in a control group. The test was positive in 11 myasthenics: the amplitude and frequency of nystagmus beats increased and extinction at the end of the test was absent or diminished. In the control group the test was negative, with the exception of 3 cases in which a slight increase in amplitude and frequency was observed. The authors stress the advantages and disadvantages of tensilon test and state that it is diagnostically valuable in myasthenia and myasthenic syndromes in subjects sensitive to the drug.     

Hair cell heterogeneity in the goldfish saccule

A set of cytological studies performed in the utricle and saccule of Astronotus ocellatus (Teleostei, Percomorphi, Cichlidae) identified two basic types of hair cells and others with some intermediate characteristics. This paper reports on applying the same techniques to the saccule of Carassius auratus (Teleostei, Otophysi, Cyprinidae) and demonstrates similar types of hair cells to those found in Astronotus. Since Carassius and Astronotus are species of extreme taxonomic distance within the Euteleostei, two classes of mechanoreceptive hair cells are likely to represent the primitive condition for sensory receptors in the euteleost inner ear and perhaps in all bony fish ears.