The effects of high- and low-intensity percutaneous stimulation on nitric oxide levels and spike activity in the superficial laminae of the spinal cord

Nitric oxide (NO) was measured using a new electrochemical method with a carbon fibre microelectrode at depths of up to 400 microm in the lumbar dorsal horn of the anaesthetised rat. The method allowed extracellular spike recording from single units together with the electrochemical recording at the same electrode. Thirty-six cells with low threshold cutaneous (brush/touch) or wide dynamic range receptive fields (brush/touch plus pinch) were studied. Adequate stimulation of the receptive fields did not alter the extracellular NO level for any cells. Percutaneous needle electrodes inserted into the receptive fields were used to stimulate the cells electrically. Twenty-one cells were stimulated using 10 mA current with 0.05 ms duration (low intensity) pulses to stimulate predominantly A-fibre afferents. Single shock stimuli gave short latency spike responses but no change in nitric oxide level. Tetanic bursts of stimuli (400 stimuli at 50 Hz) generated a burst of spikes (spike count 548+/-42) and a transient increase in NO (2.61+/-0.11 microM NO). Nitric oxide synthesis inhibition with N(G)-nitro-L-arginine methyl ester (L-NAME) nearly abolished the stimulus-evoked increase in nitric oxide and increased the response of the cells (spike count 694+/-34). However, the inhibition of nitric oxide synthesis had no effect on the receptive fields. Fifteen cells were stimulated with shocks using 5 ms pulses (high intensity), to recruit C-fibre afferents into the input volley. This more intense stimulation increased the evoked NO release to 3.63+/-0.15 microM and the spike response to 647+/-54 in control conditions. Following L-NAME, the evoked NO release was reduced and the evoked spike response was significantly decreased. These results show that tetanic activity in afferent fibres increases NO synthesis in the dorsal horn and that inhibition of nitric oxide synthesis may be associated with a selective attenuation of the spike responses to C-fibre inputs. NO may be necessary to maintain proper function of C-fibre afferent synapses when they are subjected to sustained or tetanic inputs.

Antigen-induced mucosal T cell activation is followed by Th1 T cell suppression in continuously fed ovalbumin TCR-transgenic mice

We investigated kinetics and dose-dependent features of mucosal and peripheral immune responses following oral antigen application in a TCR-transgenic mouse model. Ovalbumin (OVA) TCR-transgenic mice were fed OVA at different doses (5-250 mg) and various frequencies (one to seven times, or continuous feeding). Low- and medium-dose (10, 100 mg) OVA feeding resulted in priming of immune responses, i.e. increased antigen-specific proliferation as well as IL-2, IL-4 and IFN-gamma secretion upon in vitro restimulation in Peyer's patches and spleen. Immune responses were suppressed with doses of one or three times 250 mg OVA feeding in the spleen. However, only the highest OVA feeding doses (7x250 mg OVA) or continuous feeding (5 mg daily in the drinking water over a 12-week period) actively suppressed immune responses and were associated with production of TGF-beta and IL-10 in the spleen and Peyer's patches. Thus, the cell population generated by continuous antigen feeding was characterized by production of suppressive cytokines and seems to be based on a counter-regulation with Th1 cytokines. These data further define the regulation of suppressive immune functions following antigen feeding in the periphery and the mucosal immune system.

Two homeobox genes define the domain of EphA3 expression in the developing chick retina

Graded expression of the Eph receptor EphA3 in the retina and its two ligands, ephrin A2 and ephrin A5 in the optic tectum, the primary target of retinal axons, have been implicated in the formation of the retinotectal projection map. Two homeobox containing genes, SOHo1 and GH6, are expressed in a nasal-high, temporal-low pattern during early retinal development, and thus in opposing gradients to EphA3. Retroviral misexpression of SOHo1 or GH6 completely and specifically repressed EphA3 expression in the neural retina, but not in other parts of the central nervous system, such as the optic tectum. Under these conditions, some temporal ganglion cell axons overshot their expected termination zones in the rostral optic tectum, terminating aberrantly at more posterior locations. However, the majority of ganglion cell axons mapped to the appropriate rostrocaudal locations, although they formed somewhat more diffuse termination zones. These findings indicate that other mechanisms, in addition to differential EphA3 expression in the neural retina, are required for retinal ganglion axons to map to the appropriate rostrocaudal locations in the optic tectum. They further suggest that the control of topographic specificity along the retinal nasal-temporal axis is split into several independent pathways already at a very early time in development.

Antigen-induced mucosal T cell activation is followed by Th1 T cell suppression in continuously fed ovalbumin TCR-transgenic mice

We investigated kinetics and dose-dependent features of mucosal and peripheral immune responses following oral antigen application in a TCR-transgenic mouse model. Ovalbumin (OVA) TCR-transgenic mice were fed OVA at different doses (5-250 mg) and various frequencies (one to seven times, or continuous feeding). Low- and medium-dose (10, 100 mg) OVA feeding resulted in priming of immune responses, i.e. increased antigen-specific proliferation as well as IL-2, IL-4 and IFN-gamma secretion upon in vitro restimulation in Peyer's patches and spleen. Immune responses were suppressed with doses of one or three times 250 mg OVA feeding in the spleen. However, only the highest OVA feeding doses (7x250 mg OVA) or continuous feeding (5 mg daily in the drinking water over a 12-week period) actively suppressed immune responses and were associated with production of TGF-beta and IL-10 in the spleen and Peyer's patches. Thus, the cell population generated by continuous antigen feeding was characterized by production of suppressive cytokines and seems to be based on a counter-regulation with Th1 cytokines. These data further define the regulation of suppressive immune functions following antigen feeding in the periphery and the mucosal immune system.

Engineering the active center of the 6-phospho-beta-galactosidase from Lactococcus lactis

Several amino acids in the active center of the 6-phospho-beta-galactosidase from Lactococcus lactis were replaced by the corresponding residues in homologous enzymes of glycosidase family 1 with different specificities. Three mutants, W429A, K435V/Y437F and S428D/ K435V/Y437F, were constructed. W429A was found to have an improved specificity for glucosides compared with the wild-type, consistent with the theory that the amino acid at this position is relevant for the distinction between galactosides and glucosides. The k(cat)/K(m) for o-nitrophenyl-beta-D-glucose-6-phosphate is 8-fold higher than for o-nitrophenyl-beta-D-galactose-6-phosphate which is the preferred substrate of the wild-type enzyme. This suggests that new hydrogen bonds are formed in the mutant between the active site residues, presumably Gln19 or Trp421 and the C-4 hydroxyl group. The two other mutants with the exchanges in the phosphate-binding loop were tested for their ability to bind phosphorylated substrates. The triple mutant is inactive. The double mutant has a dramatically decreased ability to bind o-nitrophenyl-beta-D-galactose-6-phosphate whereas the interaction with o-nitrophenyl-beta-D-galactose is barely altered. This result shows that the 6-phospho-beta-galactosidase and the related cyanogenic beta-glucosidase from Trifolium repens have different recognition mechanisms for substrates although the structures of the active sites are highly conserved.

Propofol decreases stimulated dopamine release in the rat nucleus accumbens by a mechanism independent of dopamine D2, GABAA and NMDA receptors

Although propofol (2,6-di-isopropylphenol) is a popular i.v. general anaesthetic, it has been suggested to have abuse potential. As many drugs of abuse act preferentially via release of dopamine in the limbic system, we investigated the action of propofol on stimulated dopamine release in the rat nucleus accumbens. Nucleus accumbens slices were superfused (1.6 ml min-1) with artificial cerebrospinal fluid at 32 degrees C. Dopamine release was evoked by electrical stimulation (10 pulses, 0.1 ms, 10 mA, 10 Hz, every 10 min) and monitored by fast cyclic voltammetry. Propofol 100 mumol litre-1 reduced stimulated dopamine release over the 2 h after administration, relative to intralipid controls, to mean 30 (SEM 2)% (P < 0.01). The dopamine D2 receptor antagonist metoclopramide 0.3 mumol litre-1 increased dopamine release but did not block the effect of propofol (38 (3)%). The selective GABAA antagonist bicuculline 24 mumol litre-1 also failed to antagonize the action of propofol (45 (3)%). The NMDA receptor antagonist dextromethorphan 10 mumol litre-1 decreased dopamine release to 57 (6)% (P < 0.01) but failed to block the inhibitory effect of propofol (46 (6)%). Although propofol has been reported to bind to D2, GABAA and NMDA receptors, failure of metoclopramide and bicuculline to block its effects suggests that an agonist action at D2 or GABAA receptors does not mediate the effects of propofol on dopamine release in the rat nucleus accumbens. The lack of effect of dextromethorphan makes an NMDA receptor antagonist action unlikely.

Misexpression of the Emx-related homeobox genes cVax and mVax2 ventralizes the retina and perturbs the retinotectal map

The mechanisms that establish the dorsal-ventral (D-V) axis of the eye are poorly understood. We isolated two homeobox genes from mouse and chicken, mVax2 and cVax, whose expression during early eye development is restricted to the ventral retina. In chick, ectopic expression of either Vax leads to ventralization of the early retina, as assayed by expression of the transcription factors Pax2 and Tbx5, and the Eph family members EphB2, EphB3, ephrinB1, and ephrinB2, all of which are normally dorsally or ventrally restricted. Moreover, the projections of dorsal but not ventral ganglion cell axons onto the optic tectum showed profound targeting errors following cVax misexpression. mVax2/cVax thus specify positional identity along the D-V axis of the retina and influence retinotectal mapping.

Tailor-made and standardized therapy: complementary tasks in behavior therapy. A contrarian view

In medicine, decisions about treatment selection are mainly based on clinical diagnoses, whereas behavior therapists have typically assumed that it is necessary to tailor treatments based on individual problem analyses. However, various studies (including our own using patients with phobic anxieties) have failed to demonstrate an advantage for this procedure. At least for some disorders, clinical diagnosis appears to be a relevant and sufficient criterion for treatment selection. A process model is presented that views treatment individualization and standardization as complementary strategies. Although the application of techniques should be standardized as much as possible, translating general method rules into a concrete intervention for a particular person will remain a task of individualization. Individualization will also remain necessary for the other primary task of the therapist: promoting basic patient behavior that is conducive to treatment and a precondition for the successful application of interventions.

Properties of the human nuclear protein p85Mcm. Expression, nuclear localization and interaction with other Mcm proteins

Recently we identified a cDNA fragment encoding a conserved part of a new human minichromosome maintenance (Mcm) protein, provisionally termed P1.1Mcm3. Here, we report that the protein is most highly related to a yeast cell-division-cycle protein, Cdc47, encoded by the open reading frame YBR1441 on chromosome 11 of Saccharomyces cerevisiae. The human protein migrates on a polyacrylamide gel with an apparent molecular mass of 85 kDa and shares areas of significant similarity with the Mcm family of replication proteins. It is, therefore, designated as p85Mcm. Microscopic immuno-fluorescence studies revealed that protein p85Mcm is located in the nuclei of interphase cells, but is evenly distributed throughout the cell during mitosis. The amounts of p85Mcm do not significantly change during the cell cycle, but mRNA levels rise with the beginning of the S phase. However, in vitro differentiation of HL60 cells results in a striking decrease of both p85Mcm mRNA and protein levels, suggesting a role for p85Mcm in proliferating, but not in differentiated cells. Under physiological salt conditions, p85Mcm is a component of a high molecular-mass complex including other Mcm proteins. The complex dissociates at high ionic strength giving rise to stable subcomplexes, one of which contains protein p85Mcm together with Mcm proteins hCdc21 and p1O5Mcm.

A human homologue of the yeast replication protein Cdc21. Interactions with other Mcm proteins

We present the amino acid sequence of the human homologue of the yeast replication protein Cdc21, a member of the Mcm family of nuclear proteins. Specific antibodies, raised against protein hCdc21, were used to investigate the expression of the protein through the cell cycle. The protein is highly phosphorylated in mitotic cells. The phosphorylated form of protein hCdc21 appears to be less tightly bound to nuclear structures than the underphosphorylated form suggesting that phosphorylation/dephosphorylation reactions may determine the nuclear distribution of the protein. Protein hCdc21 forms a stable trimeric complex with two novel human Mcm proteins, p85Mcm and p105Mcm. Protein BM28/Mcm2 is more loosely associated with the trimeric hCdc21 complex.

Expression, phosphorylation and nuclear localization of the human P1 protein, a homologue of the yeast Mcm 3 replication protein

The human protein P1 belongs to a newly discovered class of mammalian nuclear proteins with high sequence homology to yeast replication proteins. We present the entire amino acid sequence of the human protein P1 as predicted from the cDNA sequence, and show that P1 shares three central regions of high sequence similarity (about 75%) and a highly hydrophilic carboxy-terminal region with the yeast Mcm3 replication protein. The human genome most probably contains one P1 gene which is activated when HeLa cells progress to S phase, as shown by a several-fold increase in P1-specific mRNA. However, the amounts of P1 protein do not detectably change during this period, but P1 protein becomes phosphorylated at the beginning of S phase. In contrast to the yeast Mcm proteins, which disappear from nuclei after initiation of DNA replication, protein P1 remains in the nucleus during and after S phase. P1 is dispersed in mitotic cells and may be excluded from binding to chromosomes.

Interactions of human nuclear proteins P1Mcm3 and P1Cdc46

Human nuclear proteins P1Mcm3 and P1Cdc46 have high sequence similarities with the corresponding yeast proteins known to be required for the initiation of genome replication. Nuclei of proliferating HeLa cells contain relatively high amounts of P1Mcm3 (about 10(6) molecules/nucleus) of which only a small fraction is bound to a nuclear structure, most probably chromatin. At 0.5 M NaCl, the structure-bound nuclear protein can be partially solubilized as a dimer composed of P1Mcm3 and the related protein P1Cdc46. However, most protein P1Mcm3 is not bound to a nuclear structure and appears in the nucleoplasm. About 10% of protein P1Mcm3 in the soluble fraction is free and uncomplexed, and the remaining P1Mcm3 forms stable complexes with protein P1Cdc46. These P1Mcm3/Cdc46 complexes occur as dimers and in high-molecular-mass complexes (approximately 500 kDa). The high-molecular-mass complexes dissociate in 0.5 M NaCl and release P1Mcm3/Cdc46 dimers. It has frequently been proposed that the Mcm proteins may function as licensing factors for genome replication. Our data imply that the active form of an Mcm protein is not a monomer, but a protein complex that includes an Mcm3/Cdc46 dimer. DNA polymerase alpha is not a component of this complex.