UMLS:C0011570 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0011570 (depression)
172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inhibition of the growth of nerve fibers by mercurials was quantitatively estimated by measuring the length of fibers in the cultured chick dorsal root ganglion. Morphological changes in nonneuronal cells were also evaluated. The growth rates of nerve fibers were constant for 2 to 6 days after the start of incubation. Methylmercury depressed nerve fiber growth dose- and time-dependently by 50% and completely at 3 x 10(-6) M and 7 x 10(-6) M, respectively. About 10-fold higher concentrations of inorganic mercury were required for the same extent of inhibition. The nerve fibers exposed to inorganic mercury shrank at an early stage of exposure and thereafter grew again within 24 hours. Electron microscopic examination revealed that methylmercury decreased microtubule mass extensively in nerve fibers, while inorganic mercury markedly altered surface membrane structure. These results suggested that microtubule disruption is involved in methylmercury-induced depression of nerve fibers but not in that induced by inorganic mercury. Characteristic effects on the growth of nerve fibers and the proliferation of nonneuronal cells were observed on the treatment with other metals such as cadmium, silver and chromium. Thus, dorsal root ganglion culture seems to be useful for the evaluation of toxic effects of metals in vitro.
...
PMID:Effects of methylmercury and inorganic mercury on the growth of nerve fibers in cultured chick dorsal root ganglia. 1124 49

To examine possible interactions between fast depression and modulation of inhibitory synaptic transmission in the hippocampus, we recorded from pairs of synaptically connected basket cells (BCs) and granule cells (GCs) in the dentate gyrus of rat brain slices at 34 degrees C. Multiple-pulse depression (MPD) was examined in trains of 5 or 10 inhibitory postsynaptic currents (IPSCs) evoked at frequencies of 10-100 Hz under several conditions that inhibit transmitter release: block of voltage-dependent Ca2+ channels by Cd2+ (10 microM), activation of gamma-amino-butyric acid type B receptors (GABA(B)Rs) by baclofen (10 microM) and activation of muscarinic acetylcholine receptors (mAchRs) by carbachol (2 microM). All manipulations led to a substantial inhibition of synaptic transmission, reducing the amplitude of the first IPSC in the train (IPSC1) by 72%, 61% and 29%, respectively. However, MPD was largely preserved under these conditions (0.34 in control versus 0.31, 0.50 and 0.47 in the respective conditions at 50 Hz). Similarly, a theta burst stimulation (TBS) protocol reduced IPSC1 by 54%, but left MPD unchanged (0.40 in control and 0.39 during TBS). Analysis of both fractions of transmission failures and coefficients of variation (CV) of IPSC peak amplitudes suggested that MPD had a presynaptic expression site, independent of release probability. In conclusion, different types of presynaptic modulation of inhibitory synaptic transmission converge on a reduction of synaptic strength, while short-term dynamics are largely unchanged.
...
PMID:Presynaptic short-term depression is maintained during regulation of transmitter release at a GABAergic synapse in rat hippocampus. 1185 May 13

Arsenite and cadmium are two potent nephrotoxicants and common Superfund site elements. These elements are included among the stress protein inducers, but information regarding relationships between toxicity produced by combinations of these agents to the stress protein response is lacking. In this study, the immortalized cell lines normal rat kidney NRK-52E and human kidney HK-2 were exposed in vitro to arsenite (As(3+)), cadmium (Cd(2+)), or to equimolar As(3+) plus Cd(2+) mixture combinations for 3 and 5 h over a concentration range of 0.1-100 microM. After a 12-h recovery period, cultured cells were then evaluated for expression of the 60, 70, and 90 kDa major stress protein families. Results indicated that expression of stress proteins varied depending on the species of kidney cells exposed, the exposure concentrations, and the length of exposure to each element on an individual basis and for combined mixtures. For the HK-2 kidney cell line, increased levels of the 70 kDa stress protein was observed for single and combined element exposures whereas there was no change or a decrease of stress proteins 60 and 90 kDa. Increased 70 kDa expression was observed for 10-microM doses of single elements and for a lower dose of 1 microM of the As plus Cd mixture at 3- and 5-h exposures. NRK-52 kidney cells exposed to equivalent doses of As(3+) and Cd(2+) alone or in combination showed increased levels of all stress proteins 60, 70, and 90 kDa. This increase was seen for 10 microM of the As plus Cd mixture at 3 h whereas for single element exposures, increased stress protein levels were generally observed for the 100-microM doses. At 5 h- exposure, 60 and 90 kDa levels increased for 10 microM of Cd(2+) and 60 kDa levels increased for 1 microM of As(3+). However, exposures to 10 microM of the As plus Cd mixture decreased 60 kDa protein expression to control levels at 5 h. For both kidney cell lines, there was a decrease in the stress protein expression levels for all three stress protein families for 100-microM doses of the mixture combination for 3- and 5-h exposures. These data indicate a dose- and combination-related correlation between depression of the stress protein response and the onset of overt cellular toxicity and/or cell death. The threshold for these changes was cell line specific.
...
PMID:A comparison of 60, 70, and 90 kDa stress protein expression in normal rat NRK-52 and human HK-2 kidney cell lines following in vitro exposure to arsenite and cadmium alone or in combination. 1185 74

Neurons in the nucleus laminaris detect the coincidence of binaural signals, and are the first neurons to calculate the interaural time difference for the sound source localization in birds. In this paper, we have studied contributions of synaptic depression to the coincidence detection in the nucleus laminaris in a slice preparation of the chick embryo (E16-18), using the whole-cell patch recording technique. Under voltage clamp, EPSCs decreased progressively in their amplitude during the course of tetanic stimuli. This synaptic depression was primarily ascribed to the reduction of transmitter release from the presynaptic terminal, because the depression was decreased by reducing transmitter release with 2.5 microm Cd2+ but was not affected by reducing desensitization of postsynaptic AMPA receptors with 20 microm cyclothiazide. Under current clamp, trains of 10 stimuli of 100 Hz were applied bilaterally with changing the time intervals systematically between both sides. Response window, defined as the time interval corresponding to the half-maximum firing probability, was narrowed during the course of the stimulus train, and this occurred in parallel with a decrease in the EPSP amplitude. In addition, the reduction of the EPSP amplitude due to 2.5 microm Cd2+ or 2 microm CNQX improved the accuracy of coincidence detection. These results indicate that the synaptic depression may improve the coincidence detection in the chick laminaris neurons.
...
PMID:Synaptic depression improves coincidence detection in the nucleus laminaris in brainstem slices of the chick embryo. 1191 58

The deafness (dn/dn) mutant mouse provides a valuable model of human congenital deafness. We investigated the properties of synaptic transmission in the anteroventral cochlear nucleus (AVCN) of normal and congenitally deaf dn/dn mice. Excitatory postsynaptic currents (EPSCs) were evoked by focal stimulation of single auditory nerve fibres, and measured by whole-cell recordings from neurones in AVCN slices (mean postnatal age = P13). Absolute amplitudes of both AMPA- and NMDA-mediated components of evoked EPSCs were greater (170 %) in deaf versus control animals. Enhanced transmission in deaf mice was due to a presynaptic mechanism. Variance-mean analysis revealed that the probability of transmitter release was significantly greater in deaf (P(r) = 0.8) versus control animals (P(r) = 0.5). Following high frequency stimulation, deaf mice showed a greater depression of evoked EPSCs, and a significant increase in the frequency of delayed-release (asynchronous) miniature EPSCs (aEPSCs) (deaf 100 Hz vs. control 7 Hz). The acetoxymethyl ester of EGTA (EGTA-AM) blocked the increase in miniature aEPSCs and returned tetanic depression to control values. In deaf mice, reduction of mean P(r) using cadmium caused an expected increase in paired-pulse ratio (PPR). However, in the same cells, a similar reduction in release by EGTA-AM did not result in a change in PPR, demonstrating that a change may occur in P(r) without a concomitant change in PPR. In many respects, transmission in deaf mice was found to be remarkably similar to control mice, implying that many parameters of synaptic transmission develop normally in these animals. The two significant differences (higher P(r) and asynchronous release in deaf mice) could both be reversed by the addition of EGTA-AM, suggesting that endogenous calcium buffering may be impaired or undeveloped in the presynaptic terminals of the auditory nerve in deaf mice.
...
PMID:Synaptic transmission in the auditory brainstem of normal and congenitally deaf mice. 1195 35

Purkinje cells, the output neurons of the cerebellar cortex, receive inhibitory input from basket, stellate and neighbouring Purkinje cells. The aim of the present study was to clarify the role of GABAB receptors on neurons giving inhibitory input to Purkinje cells. In sagittal slices prepared from the cerebellar vermis of the rat, the GABAB receptor agonist baclofen lowered the frequency and amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) recorded in Purkinje cells. These effects were prevented by the GABAB receptor antagonist CGP 55845. Two mechanisms were involved in the depression of the inhibitory input to Purkinje cells. The first mechanism was suppression of the firing of basket, stellate and Purkinje cells. The second mechanism was presynaptic inhibition of GABA release from terminals of the afferent axons. This was indicated by the finding that baclofen decreased the amplitude of IPSCs occurring in Purkinje cells synchronously with action potentials recorded in basket cells. A further support for the presynaptic inhibition is the observation that baclofen decreased the amplitude of autoreceptor currents which are due to activation of GABAA autoreceptors at axon terminals of basket cells by synaptically released GABA. The presynaptic inhibition was partly due to direct inhibition of the vesicular release mechanism, because baclofen lowered the frequency of miniature IPSCs recorded in Purkinje cells in the presence of cadmium and in the presence of tetrodotoxin plus ionomycin. The results show that activation of GABAB receptors decreased GABAA receptor-mediated synaptic input to cerebellar Purkinje cells both by lowering the firing rate of the inhibitory input neurons and by inhibiting GABA release from their axon terminals with a presynaptic mechanism.
...
PMID:Analysis of the function of GABA(B) receptors on inhibitory afferent neurons of Purkinje cells in the cerebellar cortex of the rat. 1205 65

Throughout the developing nervous system, immature circuits generate rhythmic activity patterns that influence the formation of adult networks. The cellular mechanisms underlying this spontaneous, correlated activity can be studied in dissociated neuronal cultures. Using calcium imaging and whole cell recording, we showed that cultured dissociated mammalian retinal neurons form networks that produce spontaneous, correlated, highly periodic activity. As the culture matures, the spatial correlations of the periodic calcium transients evolve from being highly synchronized across neighboring cells to propagating across the culture in a wavelike manner reminiscent of retinal waves recorded in vivo. Spontaneous calcium transients and synaptic currents were blocked either by cadmium, tetrodotoxin, or the glutamate receptor antagonist 6,7-dinitroquinoxaline, indicating that the periodic activity was driven primarily by synaptic transmission between retinal ganglion cells. Evoked responses between pairs of ganglion cells exhibited paired-pulse synaptic depression, and the time constant of recovery from this depression was similar to the interval between periodic events. These results suggest that synaptic depression may regulate the frequency of network activity. Together, these findings provide insight into how networks containing primarily excitatory connections generate highly correlated activity.
...
PMID:Dissociated retinal neurons form periodically active synaptic circuits. 1209 44

To date, studies on genetic variability in the tolerance of aquatic biota to chemicals have focused on exposure to single chemicals. In the field, metals occur as elemental mixtures, and thus it is essential to study whether the genetic consequences of exposure to such mixtures differs from response to single chemicals. This study determined the feeding responses of three Daphnia magna Straus clones exposed to Cd and Zn, both individually and as mixtures. Tolerance to mixtures of Cd and Zn was expressed as the proportional feeding depression of D. magna to Cd at increasing zinc concentrations. A quantitative genetic analysis revealed that genotype and genotype x environmental factors governed population responses to mixtures of both metals. More specifically, genetic variation in tolerance to sublethal levels of Cd decreased at those Zn concentrations where there were no effects on feeding, and increased again at Zn concentrations that affected feeding. The existence of genotype x environmental interactions indicated that the genetic consequences of exposing D. magna to mixtures of Cd and Zn cannot be predicted from the animals' response to single metals alone. Therefore, current ecological risk assessment methodologies for predicting the effects of chemical mixtures may wish to incorporate the concept of genetic variability. Furthermore, exposure to low and moderate concentrations of Zn increased the sublethal tolerance to Cd. This induction of tolerance to Cd by Zn was also observed for D. magna fed algae pre-loaded with both metals. Furthermore, in only one clone, physiological acclimatization to zinc also induced tolerance to cadmium. These results suggest that the feeding responses of D. magna may be related to gut poisoning induced by the release of metals from algae under low pH conditions. In particular, both induction of metallothionein synthesis by Zn and competition between Zn and Cd ions for uptake at target sites on the gut wall may be involved in determining sublethal responses to mixtures of both metals.
...
PMID:Genetic variability in sublethal tolerance to mixtures of cadmium and zinc in clones of Daphnia magna Straus. 1220 89

There is dose-dependent Cd(2+)-evoked swelling of isolated rat liver mitochondria energized by complex I, II, or IV respiratory substrates in sucrose medium in the absence of added Ca(2+) and P(i), which is prevented by Sr(2+). Permeability transition effectors (ADP, CsA, EGTA, RR, DTT, ATR, P(i), and Ca(2+)) affect in a corresponding way Cd(2+)-promoted membrane permeabilization in NH(4)NO(3), KCl, and sucrose media. Maximal depression of Cd(2+)-induced swelling is achieved by simultaneous addition of ADP, Mg(2+), and CsA that produces either synergistic (NH(4)NO(3)) or additive (KCl and sucrose media) action. Sustained activation by low [Cd(2+)] of mitochondrial basal respiration in KCl medium is observed both in the absence and in the presence of rotenone and/or oligomycin but only in the latter case (rotenone+oligomycin) CsA inhibits completely Cd(2+) activation of St 4 respiration and partially reverses DNP-uncoupled respiration depressed by cadmium. Cd(2+) effects are discussed in terms of comparison with those of Zn(2+) and PhAsO.
...
PMID:Cyclosporin A-sensitive permeability transition pore is involved in Cd(2+)-induced dysfunction of isolated rat liver mitochondria: doubts no more. 1222 May 40

The presence of chemical contaminants in marine coastal waters is a major subject of concern since many molecules are potentially immunotoxic, even at low concentration. During the last decade, studies in sentinel species, such as the blue mussel, Mytilus edulis, or the Pacific oyster, Crassostrea gigas, have revealed that immunosuppressive responses can be related to xenobiotic exposure, in the laboratory and in the field. In the present study, European flat oysters were experimentally exposed to heavy metals, to investigate possible alterations of their immune function. Several hematological and functional parameters of hemocytes were measured by flow cytometry, a technique allowing rapid, sensitive, cell-by-cell measurements in large cell populations. Results reveal a depression of phagocytosis and several subcellular, physiological changes in oysters exposed to cadmium alone or to cadmium and copper, suggesting an overall alteration of the phagocytic function.
...
PMID:Xenobiotic-induced immunomodulation in the European flat oyster, Ostrea edulis. 1240 22

<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>