Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Stable intracellular recordings were obtained from neurones in slices of the guinea-pig olfactory cortex maintained in vitro. 2. Single stimuli applied to the lateral olfactory tract (l.o.t.) produced an excitatory post-synaptic potential (e.p.s.p.) usually generating a single spike. 3. The e.p.s.p. was followed by a long (200-500 msec) after-depolarization (l.a.d.) of peak amplitude 5-16 mV. This was accompanied by a very large conductance increase and was associated with an inhibition of the intracellularly recorded e.p.s.p. and of spike generation. 4. The l.a.d. was more susceptible than the e.p.s.p. to depression by (i) repetitive l.o.t. stimulation and (ii) raising external [Mg2+]. The l.a.d. could be generated without a preceding spike. 5. At an average resting membrane potential of -74 mV the average reversal potential for the l.a.d. (El.a.d.) was -63 mV.El.a.d. became more positive on reducing [Cl-]out or on using KCl-filled electrodes. 6. It is concluded that the l.a.d. represents a Cl- -mediated inhibitory post-synaptic potential, generated through deep-lying recurrent inhibitory loops.
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PMID:A depolarizing inhibitory potential in neurones of the olfactory cortex in vitro. 63 55

We measured plasma concentrations of Na+, K+, Mg2+, Cl-, Ca2+, HCO3-, phosphate, lactate, glucose, total amino acids, and total protein, and also the total (freezing point depression) osmolality and the colloid osmotic pressures. Conversion of chemically measured concentrations to osmolalities showed that unrecognized solute (s) were present in maternal (7 mM) and fetal (12 mM) plasma. Statistically reliable transplacental gradients existed only for calcium ion, phosphate, and amino acids, Ionic Na, K Mg, Cl, Ca, HCO3 and lactate were in electrochemical equilibrium at potential differences of -4.2 to +1.3 mV. Total plasma osmolalities were not significantly different in maternal and fetal plasmas in preparations in good condition, but fetal plasma osmolalities rose due to lactate secretion in asphyxiated fetuses. Colloid osmotic pressures were about 5 cmH2O higher in maternal plasmas before 45 days gestation and about 6 cmH2O higher in fetal plasmas after 60 days gestation. In the guinea pig, colloid osmotic pressures are at least as important as intravascular pressures in the regulation of transplacental water flow.
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PMID:Transplacental gradients in the guinea pig. 68 87

Magnesium ion (Mg2+) in concentrations of 5-10 micron has been used to block synaptic transmission in in vitro preparations of central nervous system tissue. We have used explants of mouse cerebellum grown in culture to test whether significant levels of direct depression of neuronal membrane excitability could occur in such experiments. Using thresholds for antidromic activation and iontophoretically applied glutamate as tests of excitability, potent depressions of membrane excitability were found using 5-10 micron Mg2+. The additive depressant effects of increased Ca2+ concentrations provided further evidence that the effects were largely on membrane excitability and not on transmitter release mechanisms.
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PMID:Depression by magnesium ion of neuronal excitability in tissue cultures of central nervous system. 88 93

L5178Y mouse lymphoma cells normally appear to possess two functional thymidine kinase alleles (TK+/+). TK-deficient (TK-/-) clonal lines can be derived from these cells by treatment with EMS or other mutagens. Mezger-Freed [12] has argued that such stable phenotypic variants do not arise as the result of gene mutations but instead represent epigenetic events such as normally occur during differentiation without any permanent gene alteration. If this be so, then rare TK+/- revertants arising in TK-/- cultures should possess TK enzyme identical with one of those present in the original TK+/+ cells, since only depression of the TK gene is involved. Our studies show that this is not the case. Among the mutant TK enzymes analyzed in vitro (those from parental TK+/- lines, each derived in turn from separate TK-/- lines) differences were found in (1) solubility in saline; (2) solubility in 3 M LiCl; (3) Km's; and (4) ATP-Mg2+ requirements. These findings were incompatible with a non-mutational model for the production of these stable variants and, in conjunction with reversion-rate data, they tended to favor either direct structural gene modifications or mutations affecting the expression of adult and fetal enzymes.
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PMID:Evidence for chemically-induced structural gene mutations at the thymidine kinase locus in cultured L5178Y mouse lymphoma cells. 89 58

1. A circuit that produces a 70-100 ms IPSP in the crayfish giant motoneuron is described. The IPSP is produced by a disynaptic pathway from the nongiant fast flexor motoneurons to the motor giant. 2. An inhibitory interneuron in the pathway has been identified. Its axon runs at least the entire length of the abdominal nervous system. The inhibitory interneuron is excited bilaterally in all abdominal ganglia except the last and bilaterally inhibits the motor giants thoughout the abdominal CNS. 3. Evidence for a monosynaptic connection between the interneuron and the motor giant includes short latency, stability during repetitive stimulation, gradual decrement in high-Mg2+ solutions, and persistence in high-Ca2+ solutions. Similar but less complete evidence suggests a monosynaptic connection from the fast flexor motoneurons to the inhibitory interneuron. 4. A single impulse in the inhibitor can produce a prolonged IPSP in the motor giant. The inhibitor did not display trains of impulses and was not spontaneously active. 5. The inhibitory interneuron appears to be highly specific; no other outputs were observed. 6. Direct stimulation of axons in the connectives suggests that four pairs of inhibitory interneurons converge on the motor giants; at least two pairs are activated by the fast flexor motoneurons. 7. This circuit limits the burst duration of the motor giant and may function to protect the motor giant's depression-prone neuromuscular junction.
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PMID:Neuronal organization of crayfish escape behavior: inhibition of giant motoneuron via a disynaptic pathway from other motoneurons. 90 98

Magnesium absorption was studied in the normal human jejunum and ileum by in vivo intestinal perfusion, using test solutions containing from 0 to 20 mM Mg (as MgCl2). As luminal Mg concentration was increased, the rate of absorption in the jejunum rose progressively with a tendency towards saturation at the higher concentrations. The kinetics and rates of Mg absorption in the ileum were comparable to those in the jejunum, with the exception that at higher luminal concentrations the ileal absorptive process was fully saturated. Using test solutions containing various combinations of Ca and Mg, we found that Ca had little or no influence on Mg absorption, even through Mg depressed Ca absorption to a modest extent. Patients with end-stage renal disease, who had a reduced rate of Ca absorption (presumably due to deficiency of 1,25-dihydroxycholecalciferol) were found to have a severe depression of Mg absorption. On the other hand, patients with absorptive hypercalciuria and nephrolithiasis, who had an increased rate of Ca absorption, were found to absorb Mg normally. These results suggest that Mg absorption in the human is mediated by a transport process different from that which facilitates Ca absorption, and that normal Mg absorption may be dependent on vitamin D. Our results do not establish whether or not the normal intestine can absorb Mg against an electrochemical gradient.
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PMID:Magnesium absorption in the human small intestine. Results in normal subjects, patients with chronic renal disease, and patients with absorptive hypercalciuria. 93 89

1. The negative (N)-wave evoked at various depths in the cuneate nucleus by stimulation of afferents in the ipsilateral forepaw or dorsal column has been studied in the rat. 2. Micro-iontophoretic applications of gamma-aminobutyric acid (GABA) into the vicinity of the recording electrode markedly reduced the amplitude of the negative wave, but only when recordings were made near the base of the cuneate nucleus. Nearer the surface of the medulla, GABA was much less effective. 3. A similar depth distribution obtained for the depression of the negative wave by micro-iontophoretic Mg2+ and enhancement by Ca2+. 4. Depression of the negative wave by conditioning stimulation of the afferent pathway also showed a similar depth distribution. The conditioned depression of the negative wave was most marked during the first 30 ms after the conditioning stimulus and this early depression could be antagonized by iontophoretic (+)-bicuculline methochloride. A lesser degree of conditioned inhibition of the negative wave persisted up to 80-200 ms but this was resistant to (+)-bicuculline methochloride. Thus, conditioned depression of the negative wave appeared to be mediated only in part by a GABA-like transmitter. 5. It is concluded that the negative wave recorded near the base of the cuneate nucleus has some of the predicted properties of a post-synaptic potential. These properties are not seen when the negative wave is recorded more superficially, near the surface of the medulla.
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PMID:The negative potential wave evoked in cuneate nucleus by stimulation of afferent pathways: its origins and susceptibility to inhibition. 94 53

Although it is generally agreed that active sugar absorption in vitro is absolutely dependent on the presence of sodium ions on the luminal side of the mucosa, previous in vivo studies in the ileum of rat, dog and man have shown that active glucose absorption is almost as rapid from a sodium-free mannitol solution as from a sodium chloride solution. These experiments were performed in hopes of reconciling this discreptancy. Absorption of three actively transported sugars (glucose, galactose, and 3-O-methylglucose) having different apparent Km's, and of fructose (absorbed by a separate carrier-mediated process) were measured in the human ileum in vivo. The following observations were made: (1) Mannitol substitution for sodium results in only a slight reduction (23%) in the active absorption of glucose. (2) Magnesium substitution for sodium results in a greater depression (45%) of glucose absorption. (3) The apparent Km for glucose absorption is increased when sodium is replaced by magnesium, but the Vmax is not altered. (4) Magnesium does not depress glucose absorption or the apparent Km for glucose transport when sodium is present in the perfusing solution. (5) Neither sodium removal nor magnesium has any effect on fructose absorption. (6) Absorption of galactose and 3-O-methylglucose (low affinity sugars for the glucose carrier) is reduced by about 40 to 50% when mannitol replaces sodium, but magnesium substitution for mannitol in a sodium-free medium does not further depress absorption of these sugars. The following conclusions are suggested by these results: First, part of the discrepancy between previous in vitro and in vivo experiments was due to the type of test sugar (glucose versus glucose analogue) and the solute used to replace sodium in the luminal solution. Second, magnesium is more effective than mannitol in reducing sodium concentration at the glucose transport site on the brush border. Third, luminal sodium ions have an important effect on active sugar absorption in the human small intestine in vivo, as they do in vitro. And, fourth, there is a component of active sugar absorption (about one-half) which appears to be independent of luminal sodium ions in vivo.
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PMID:Effect of sodium, mannitol, and magnesium on glucose, galactose, 3-O-methylglucose, and fructose absorption in the human ileum. 111 66

In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control.
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PMID:Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa. 111 94

1. The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 +/- 0.28 mu-equiv cm(-2) /(-1) in 8 mM-Mg2+. 2. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 mu-equiv/g wet weight of midgut tissue. 3. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. 4. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 mu-equiv cm(-1) /(-1). 5. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.
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PMID:Active transport of magnesium across the isolated midgut of Hyalophora cecropia. 120 24


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