Dopamine D2 receptor polymorphisms in inflammatory bowel disease and the refractory response to treatment

Dopamine and its receptors may be involved in inflammatory reaction. The availability of this molecule depends on its receptors. The DRD2 gene, which codifies for the D2 dopamine receptor, has several polymorphisms. In this study, the DRD2 TaqIA polymorphism, which confers a decreased receptor density, was evaluated in 313 individuals including 220 inflammatory bowel disease patients (143 patients with Crohn's disease and 77 with ulcerative colitis) and in 93 healthy blood donors. The analysis was carried out by PCR-RFLP techniques. The frequencies of A (1) A (1) and A (2) A (2) genotypes were similar among Crohn's disease, ulcerative colitis patients, and health controls. Also, the genotype frequency was similar in different groups of disease localization, behavior, and age of disease onset. However, the Crohn's disease patients carriers of A (2) A (2) genotype showed a lower risk for development refractory Crohn's disease (37 out 65) than A (1) A (1) and A (1) A (2) carriers (28 out of 65) [(OR=0.4, 95% CI 0.21-0.87; p=0.02)]. Our results support an involvement of the dopamine receptor in inflammatory bowel disease and suggest a new potential target for therapy in refractory Crohn's disease patients.

Soluble selectins, sICAM, sVCAM, and angiogenic proteins in different activity groups of patients with inflammatory bowel disease

The endothelium is involved in the pathogenesis of inflammatory bowel disease (IBD). So far knowledge of the precise role of soluble adhesion molecules and angiogenic factors at different periods of activity in IBD is scarce or contradictory. Our goal in this study was to determine the serum levels of adhesion molecules and angiogenic factors in IBD patients at different periods of disease activity--clinical remission, biochemical evidence of inflammation, and clinical evidence of activity. We used a cross-sectional study design consisting of 218 patients (145 with Crohn's disease [CD] and 73 with ulcerative colitis [UC]) and 115 randomly assymptomatic blood donors. To assess disease activity, Harvey and Bradshaw's and Truelove-Witts' indexes were used. Circulating plasma sE-selectin (sE-S), sP-selectin (sP-S), human soluble vascular cell adhesion molecule-1 (sVCAM-1), and human soluble intercellular adhesion molecule-1 (sICAM-1) and serum levels of human vascular endothelial growth factor (VEGF), angiogenin (ANG), and placenta growth factor (P/GF) were measured with ELISAs. The amount of mRNA VEGF in blood mononuclear cells was also evaluated. In inactive CD patients, serum levels of sP-S, sE-S, sVCAM, and sICAM were significantly lower (P < 0.05) than in controls. In active CD patients, only the sE-S values were higher than in controls. In UC patients, sP-S and sVCAM levels were significantly lower than those in controls. Considering growth factors, CD patients in remission had levels of ANG and VEGF lower than those found in controls. The VEGF RNAm in blood mononuclear cells was similar among all CD activity groups. In conclusion, in UC patients the serum levels of VEGF, ANG, and P/GF were similar to those in controls. The serum levels of adhesion molecules and angiogenic factors were low in IBD patients in periods of remission. Low levels of angiogenic factors in inactive CD patients suggest dysfunction of the angiogenic process and wound repair.

Gemifloxacin inhibits cytokine secretion by lipopolysaccharide stimulated human monocytes at the post-transcriptional level

The fluroquinolone gemifloxacin was examined for its capacity to modulate secretion of cytokines by human monocytes stimulated with lipopolysaccharide (LPS). Monocytes from six male and two female healthy volunteers were stimulated with LPS, exposed to gemifloxacin and the amounts of secreted IL-1 alpha, IL-1 beta, IL-6, IL-10 and TNF-alpha measured at 3, 6 and 24 h. The results revealed that LPS alone increased secretion of each cytokine significantly. Treatment of the LPS-stimulated monocytes with gemifloxacin resulted in a significant inhibition (p < 0.01) of secretion of each of the cytokines from monocytes of the eight volunteers. Nuclear extracts of the human monocyte cell line, THP-1, were used in the electrophoretic mobility shift assay to determine whether gemifloxacin affects nuclear factor-kappa B (NF-kappa B) activation. In addition, RNA from THP-1 cells was used in Northern blots to determine whether inhibition of secretion of IL-1 beta and TNF-alpha by gemifloxacin occurred at the transcription or translation level. Whereas LPS induced a rapid increase in NF-kappa B activation, gemifloxacin alone did not. Gemifloxacin did not affect the kinetics or decrease the extent of activation. Northern blots indicated that the inhibitory activity of gemifloxacin occurred post-transcription. Thus, gemifloxacin may modulate the immune response by altering secretion of cytokines by human monocytes. Although the concentrations of gemifloxacin used were higher than those observed in the serum of human volunteers treated with the dose under clinical development, it should be taken into consideration that concentrations at tissue and intracellular levels may be considerably higher than serum concentrations.

[Giant evoked potentials]

INTRODUCTION

There are many, diverse nosological entities with the common factor of the genesis of cortical evoked potentials of great amplitude, commonly known as giant evoked potentials. In most cases they are conditions with the common clinical condition of myoclonic of cortical origin, such as progressive myoclonic epilepsy, generalized idiopathic epilepsy, myoclonias of toxic, infectious or postanoxic origin. Giant potentials have been shown both in studies of focal hemisphere lesions and in some cases of patients with corticobasal degeneration.

OBJECTIVE

The aim of this paper was to show, by presenting interesting cases, some of the conditions mentioned and to review some concepts concerning the mechanisms which may be involved in the production of these electrophysiological responses.

PATIENTS AND METHODS

We studied 6 patients aged between 2 and 22 years, in whom multimodal evoked potentials, electroencephalograms and imaging studies had been done.

RESULTS

Giant somatosensory potentials were shown in the patients with obvious myoclonia. Visual potentials of great amplitude were common to the other patients presented, with or without myoclonia.

CONCLUSION

Giant evoked potentials respond to a state of cortical hyperexcitability which may have various causes.

Prevalence between different alpha subunits performing the benzodiazepine binding sites in native heterologous GABA(A) receptors containing the alpha2 subunit

The presence of two heterologous alpha subunits and a single benzodiazepine binding site in the GABA(A) receptor implicates the existence of pharmacologically active and inactive alpha subunits. This fact raises the question of whether a particular alpha subtype could predominate performing the benzodiazepine binding site. The hippocampal formation expresses high levels of alpha subunits with different benzodiazepine binding properties (alpha1, alpha2 and alpha5). Thus, we first demonstrated the existence of alpha2-alpha1 (36.3 +/- 5.2% of the alpha2 population) and alpha2-alpha5 (20.2 +/- 2.1%) heterologous receptors. A similar alpha2-alpha1 association was observed in cortex. This association allows the direct comparison of the pharmacological properties of heterologous native GABA(A) receptors containing a common (alpha2) and a different (alpha1 or alpha5) alpha subunit. The alpha2 subunit pharmacologically prevailed over the alpha1 subunit in both cortex and hippocampus (there was an absence of high-affinity binding sites for Cl218,872, zolpidem and [3H]zolpidem). This prevalence was directly probed by zolpidem displacement experiments in alpha2-alpha1 double immunopurified receptors (K(i) = 295 +/- 56 nM and 200 +/- 8 nM in hippocampus and cortex, respectively). On the contrary, the alpha5 subunit pharmacologically prevailed over the alpha2 subunit (low- and high-affinity binding sites for zolpidem and [3H]L-655,708, respectively). This prevalence was probed in alpha2-alpha5 double immunopurified receptors. Zolpidem displayed a single low-affinity binding site (K(i) = 1.73 +/- 0.54 microM). These results demonstrated the existence of a differential dominance between the different alpha subunits performing the benzodiazepine binding sites in the native GABA(A) receptors.

Distribution of the gamma-aminobutyric acid(A) receptor complex alpha 5 subunit in chick brain. An immunocytochemical and autoradiographic study

This work reports the distribution of the gamma-aminobutyric acid(A) (GABA(A)) receptor complex alpha5 subunit in the chick using an antibody raised against this subunit in the rat, an immunoprecipitation study and a comparative autoradiographic study using [(3)H]flunitrazepam in the presence of 1 microM zolpidem, which is considered to bind only to those areas presenting the alpha5 subunit. The specificity of the antibody for the chick GABA(A) receptor complex alpha5 subunit is supported by the similar bands obtained by Western blotting from rat and chick, the immunoprecipitation study and the general agreement in the distribution and pattern of labelling of this antibody in both species. The immunocytochemical and autoradiographic distributions in both the chick and rat are compared and some areas with disagreement between these distributions are discussed. The general conclusion is that the alpha5 subunit of the GABA(A) complex receptor seems to have been conserved along evolution.

GABAA and alpha-amino-3-hydroxy-5-methylsoxazole-4-propionate receptors are differentially affected by aging in the rat hippocampus

We have investigated the age-dependent modifications in the expression of eight different subunits of the gamma-aminobutyric acid, type A (GABA(A)) receptor (alpha1, alpha2, alpha3, alpha5, beta2, beta3, gamma2S, and gamma2L) and all four subunits of the alpha-amino-3-hydroxy-5-methylsoxazole-4-propionate (AMPA) receptor (GluR1-4) in the hippocampus of 24-month-old rats. All aged hippocampi displayed a remarkable increase (aged/adult ratio, 3.53 +/- 0.54) in the mRNA levels of the short version of the gamma2 subunit in parallel with a similar increase in the gamma2 subunit protein (aged/adult ratio, 2.90 +/- 0.62). However, this increase was not observed in the mature receptor. On the other hand, the expression of the different alpha subunit mRNAs increased moderately with aging, displaying a heterogeneous pattern. The most frequent modification consisted in an increase in the expression of the alpha1 subunit mRNA (aged/adult ratio, 1.26 +/- 0.18), in parallel with a similar increase on the alpha1 protein (aged/adult ratio, 1. 27 +/- 0.12) and in the alpha1 incorporated to the assembled GABA(A) receptor (tested by immunoprecipitation; aged/adult ratio, = 1.20 +/- 0.10). However, in the same hippocampal samples, no major modifications were observed on the expression of the AMPA receptor subunits. As a whole, these results indicated the existence of an increased expression of the GABA(A) receptor subunits and a preservation of the AMPA receptor at the hippocampal formation. These modifications could reflect the existence of specific deficiencies (neuronal loss and/or deafferentiation) on the GABAergic system in the aged rats.

Native gamma-aminobutyric acid type A receptors from rat hippocampus, containing both alpha 1 and alpha 5 subunits, exhibit a single benzodiazepine binding site with alpha 5 pharmacological properties

Evidences indicate the existence of two homologous and/or heterologous alpha subunits coassembled in a single gamma-aminobutyric acid type A (GABA(A)) receptor. However, it is unknown whether both or only one of the coassembled alpha subunits display benzodiazepine binding sites. Thus, we have investigated the association between alpha1 and alpha5 subunits and the pharmacological properties of these GABA(A) receptors from rat hippocampus. The association between alpha1 and alpha5 subunits was demonstrated by immunoblot of the anti-alpha1 or -alpha5 immunoaffinity-purified receptors and by double immunopurification by anti-alpha1 and -alpha5 columns in series. The benzodiazepine binding properties of the immunoprecipitated receptors indicated the existence of pharmacologically active and inactive alpha subunits. The anti-alpha5 immunoprecipitated receptors displayed exclusively low-affinity binding sites for both Cl218,872 (K(i) = 0.81 +/- 0.15 microM) and zolpidem (K(i) = 5.0 +/- 3.0 microM), in spite of the association between alpha1 and alpha5 subunits. The anti-alpha1 immunoprecipitated receptors displayed both high- and low-affinity binding sites for both ligands (K(i)s = 47.5 +/- 5.2 nM and 0.7 +/- 0.06 microM for Cl218,872 and 25.0 +/- 7.0 nM, 415 +/- 200 nM and 9. 3 +/- 3.0 microM for zolpidem). Therefore, the alpha5 subunit, when coassembled with alpha1 subunit, should be pharmacologically predominant. This hypothesis was probed by immunoprecipitation of the photoaffinity-labeled receptors and by anti-alpha1 and -alpha5 double immunopurified receptors. The alpha1-alpha5 double immunopurified receptors displayed a single low-affinity binding site (K(i) = 908 +/- 105 nM) for Cl218,872, undetectable [(3)H]zolpidem binding activity, and similar [(3)H]flumazenil and [(3)H]L-655,708 binding activity (0.10 +/- 0.01 and 0.09 +/- 0.02 pmol/20 microliters of anti-alpha5 immunobeads, respectively). Thus, the native GABA(A) receptors containing alpha1 and alpha5 subunits have only one alpha subunit pharmacologically active displaying alpha5 binding properties.

Pharmacological properties of the GABA(A) receptor complex from brain regions of (hypoemotional) Roman high- and (hyperemotional) low-avoidance rats

The pharmacological properties of benzodiazepine binding sites of the gamma-aminobutyric acid (GABA)A receptor complex from cortical, hippocampal and cerebellar membranes of Roman high-avoidance (RHA/Verh) and Roman low-avoidance (RLH/Verh) rats were investigated. No major differences between the two lines were found in the binding parameters of [3H]flunitrazepam (a non-selective agonist). [3 H]zolpidem (a Type I selective agonist) or [3 H]ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazol[1,5-a]-[1,4]benzodiazepine- 3-carboxylate (Ro15-4513) (a partial inverse agonist). Neither the Kd values nor the Bmax for these ligands differed between RHA/Verh and RLA/Verh rats in any of the brain regions studied. As a result, the proportion of Type I binding sites in cortical and hippocampal membranes of RHA/Verh and RLA/Verh rats or the 'diazepam-sensitive' and the 'diazepam-insensitive' binding sites in cerebellar membranes, calculated from the [3H]flunitrazepam and [3H]zolpidem maximal binding sites or from [3H]Ro15-4513 binding (in the absence or in presence of diazepam), respectively, was also similar. Furthermore, there were no differences between the two rat lines in the allosteric interactions between GABA and the benzodiazepine binding sites (labeled with [3H]flunitrazepam) in all three areas tested or the Type I binding sites (labeled with [3H]zolpidem) in the hippocampus. In contrast, RLA/Verh rats showed a significant reduction in the allosteric interactions between GABA and [3H]zolpidem binding sites in the cortex. As a whole, these results indicate the absence of generalized between-line differences in the GABA(A) receptor complex showing, at the same time, the existence of some specific differences in allosterism within the GABA(A) complex. These differences may contribute to the divergent emotional responses which characterize the RHA/Verh and RLA/Verh rat lines.

Absence of association between delta and gamma2 subunits in native GABA(A) receptors from rat brain

We investigated the possible association between delta and gamma2 subunits in native GABA(A) receptors, from different rat brain regions, using subunit-specific anti-delta and anti-gamma2 antibodies. Previous reports have provided somewhat controversial results, indicating both the presence and the absence of association between these two subunits in native receptors. Our results indicate the absence of co-localization between delta and gamma2 subunits. In immunoprecipitation experiments, anti-delta antibody consistently immunoprecipitated [3H]muscimol binding activity (GABA binding sites) from all brain areas tested (10-20% of the total binding). However, under the same conditions, no significant [3H]flumazenil or [3H]ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazol[1,5-a]-[1,4]benzodiazepine- 3-carboxylate (Ro15-4513) binding (benzodiazepine binding sites) activity was detected in the immunopellets. These results indicate the absence of association between delta and gamma2 subunits. This question was directly addressed by immunopurification and Western blot experiments. As expected, no gamma2 subunits were detected in anti-delta immunoaffinity purified receptors. Conversely, no delta subunits were identified in anti-gamma2 immunopurified receptors. Thus, these results demonstrate the absence of association between delta and gamma2 subunits in native GABA(A) receptors. Finally, our results also indicate the relevance of the solubilization conditions on the apparent association between different subunits of the native GABA(A) receptor complex.

Chronic infection with Toxoplasma gondii does not prevent acute disease or colonization of the brain with tissue cysts following reinfection with different strains of the parasite

Two strains of Toxoplasma gondii with different capacities to induce disease and brain lesions in mice were used to study the effects of reinfection with the parasite on a previously infected host. In spite of marked antibody and cell-mediated immune responses, chronically infected mice developed disease and died of acute toxoplasmosis when reinfected with a strain different from the one causing the primary infection. Moreover, the marked antibody and cell-mediated immune responses of the chronically infected mice did not prevent invasion of their brains and formation of tissue cysts by the reinfecting strain. Tissue cysts of the reinfecting strain were demonstrated in the brains of the chronically infected and subsequently reinfected mice. These results highlight the importance of strain differences in the pathogenesis of toxoplasmosis.

GABAA receptor subunit expression changes in the rat cerebellum and cerebral cortex during aging

Significant aging-related decreased expression of various GABAAR subunit mRNAs (alpha 1, gamma 2, beta 2, beta 3 and sigma) was found in both cerebellum and cerebral cortex using quantitative dot blot and in situ hybridization techniques. Contrary to the other subunits, the alpha 6 mRNA expression was significantly increased in the aged cerebellum. Parallel age-related changes in protein expression for gamma 2 and beta 2/3 (decrease) and alpha 6 (increase) were revealed in cerebellum by quantitative immunocytochemistry. However, no significant changes in alpha 1 protein expression nor in the number or affinity of [3H]zolpidem binding sites were detected in cerebellum even though alpha 1 mRNA expression was significantly decreased in the aged rat. Age-related increased expression of alpha 6 mRNA and protein in the cerebellum was accompanied by no significant changes in the number of diazepam-insensitive [3H]Ro15-4513 binding sites. In the cerebral cortex, no changes in the protein expression of the main GABAA receptor subunits (alpha 1, gamma 2 and beta 2/3) were observed which contrasted with the age-related decreased expression of the corresponding mRNAs. No significant changes in the number or affinity of [3H]zolpidem binding sites were observed in the cerebral cortex. Thus, age-related changes in the mRNA expression of a particular subunit does not necessarily lead to similar changes in protein or assembly into mature GABAA receptors. The results reveal the existence of complex regulatory mechanisms of GABAA receptor expression, at the transcriptional, translational and post-translational and/or assembly levels, which vary with the subunit and brain area.

Molecular and pharmacological characterization of native cortical gamma-aminobutyric acidA receptors containing both alpha1 and alpha3 subunits

We have investigated the existence, molecular composition, and benzodiazepine binding properties of native cortical alpha1-alpha3 gamma-aminobutyric acidA (GABAA) receptors using subunit-specific antibodies. The co-existence of alpha1 and alpha3 subunits in native GABAA receptors was demonstrated by immunoblot analysis of the anti-alpha1- or anti-alpha3-immunopurified receptors and by immunoprecipitation experiments of the [3H]zolpidem binding activity. Furthermore, immunodepletion experiments indicated that the alpha1-alpha3 GABAA receptors represented 54.7 +/- 5.0 and 23.6 +/- 3.3% of the alpha3 and alpha1 populations, respectively. Therefore, alpha1 and alpha3 subunits are associated in the same native GABAA receptor complex, but, on the other hand, these alpha1-alpha3 GABAA receptors from the cortex constitute a large proportion of the total alpha3 population and a relatively minor component of the alpha1 population. The pharmacological analysis of the alpha1- or alpha3-immunopurified receptors demonstrated the presence of two different benzodiazepine binding sites in each receptor population with high (type I binding sites) and low (type II binding sites) affinities for zolpidem and Cl 218,872. These results indicate the existence of native GABAA receptors possessing both alpha1 and alpha3 subunits, with alpha1 and alpha3 subunits expressing their characteristic benzodiazepine pharmacology. The molecular characterization of the anti-alpha1-anti-alpha3 double-immunopurified receptors demonstrated the presence of stoichiometric amounts of alpha1 and alpha3 subunits, associated with beta2/3, and gamma2 subunits. The pharmacological analysis of alpha1-alpha3 GABAA receptors demonstrated that, despite the fact that each alpha subunit retained its benzodiazepine binding properties, the relative proportion between type I and II binding sites or between 51- and 59-61-kDa [3H]Ro15-4513-photolabeled peptides was 70:30. Therefore, the alpha1 subunit is pharmacologically predominant over the alpha3 subunit. These results indicate the existence of active and nonactive alpha subunits in the native alpha1-alpha3 GABAA receptors from rat cortex.

Age-related modifications on the GABAA receptor binding properties from Wistar rat prefrontal cortex

In the present communication we have investigated the pharmacological properties of the GABAA receptor from adult (3 months old) and aged (24 months old) Wistar rat prefrontal cortex. The prefrontal cortex is implicated in cognitive functions and stress and both processes seem to be altered during aging. These changes could be mediated by modifications in the GABAA receptor properties. Our results indicated the absence of generalized age-related modifications on the pharmacological properties of the GABAA receptor from prefrontal cortical membranes. Saturation experiments using the non-selective benzodiazepine [3H]flunitrazepam revealed that neither the Kd values or the Bmax were modified during aging. Moreover, Cl 218 872 displacement of [3H]flunitrazepam showed no age-related modifications on either the Kis or the relative proportion between the Type I and Type II benzodiazepine binding sites. Therefore, the benzodiazepine binding sites are well preserved in aged prefrontal cortex. On the other hand, saturation experiments using the GABA agonist [3H]muscimol demonstrated in the Bmax of the low affinity [3H]muscimol binding sites in aged rats (4.3 +/- 0.8 pmol/mg protein vs. 2.3 +/- 0.2 pmol/mg protein in adult and aged rats, respectively). However, no age-dependent modifications were observed in the allosteric interaction between GABA and benzodiazepine binding sites. These results demonstrate that the benzodiazepine binding sites and the GABA binding sites of the GABAA receptor complex from rat prefrontal cortical membranes are differentially affected by the aging process.

Interleukin-12-mediated resistance to Trypanosoma cruzi is dependent on tumor necrosis factor alpha and gamma interferon

The aim of this study was to determine if interleukin-12 (IL-12) has a role in the immune response to Trypanosoma cruzi. Infection of BALB/c mice with the virulent Tulahuen strain of T. cruzi is characterized by a high-level parasitemia, pathology in the heart associated with the presence of amastigotes, and death during the acute phase of the disease. Administration of IL-12 to BALB/c mice infected with T. cruzi resulted in a reduced parasitemia and a significant delay in the time to death compared with those for infected controls. This protective effect was correlated with increased levels of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) in serum. To determine if these cytokines were involved in the protective effects of IL-12, we treated infected mice with IL-12 alone or in combination with monoclonal antibodies specific for IFN-gamma or TNF-alpha. These antibodies antagonized the protective effect of exogenous IL-12. Treatment of infected mice with a polygonal antibody specific for IL-12 resulted in a significant increase in parasitemia but did not affect the time to death. These latter studies demonstrate a role for endogenous IL-12 in resistance to T. cruzi. Together, our data identify an IL-12-mediated mechanism of resistance to T. cruzi, which is dependent on IFN-gamma and TNF-alpha.

Uniject as a delivery system for the once-a-month injectable contraceptive Cyclofem in Brazil

This study assessed the administration of Cyclofem using prefilled Uniject devices. A total of 480 injections were administered divided equally between standard syringes and Uniject. The majority of women (82%) reported that they felt anxious prior to receiving the injection with Uniject. After injection, more than 80% expressed no anxiety about the appearance of Uniject or about the technique of injection. A total of 96.3% of the participants reported slight to no pain with Uniject. In comparison to the standard syringe, 5.6% expressed having had more pain with Uniject. Ninety percent of the service providers reported that Uniject was easy to activate and inject and that it was reassuring for users to know that the syringe and needle had never been used previously. Only two service providers demonstrated difficulties in activating the device. No accidental punctures occurred during the manipulation, and incomplete emptying of the Uniject was not observed. In conclusion, Uniject is a good device for the administration of the injectable contraceptive Cyclofem. It is likely to be appropriate for the delivery of other injectable contraceptives after the necessary stability tests have been performed.

Some phosphonic acid analogs as inhibitors of pyrophosphate-dependent phosphofructokinase, a novel target in Toxoplasma gondii

Pyrophosphate-dependent phosphofructokinase (PPi-PFK) was identified previously in Toxoplasma gondii as the only kinase that phosphorylates fructose-6-P to fructose-1,6-bisP. Since such an enzyme is not present in mammals, it was considered to be a good target for prospective selective inhibitors of the parasite. We have examined the effects of several phosphonic acid derivatives, analogs of pyrophosphate, on PPi-PFK activity, as well as on the replication of T. gondii in human foreskin fibroblast (HFF) cells. The most active compound in inhibiting PPi-PFK was tetrasodium carbonyldiphosphonate. Several bisphosphonates and related arylhydrazones showed inhibition of the enzyme, but with higher IC50 values. Although several phosphonoacetic acid derivatives also inhibited PPi-PFK, as a group they were less potent than the bisphosphonate derivatives. Comparison among the structures of various inhibitors and their effects against PPi-PFK indicates that a carbonyl (C=O) or amino (C=N) group between two phosphoryl moieties is associated with more potent enzyme inhibiton. Tetrasodium carbonyldiphosphonate did not show a significant effect against replication of T. gondii cells, probably because, as a charged molecule, it could not cross the cell membrane to reach the intracellular parasite. Tetraisopropyl carbonyldiphosphonate 2,4-dinitrophenylhydrazone showed some selective inhibitory effect against replication of the parasite in the HFF cells and protected the mammalian cells from damage by T. gondii. The results indicate that carbonyldiphosphonic acid is a good prototype compound that is amenable to chemical manipulation, which, in turn, may optimize selective inhibition of T. gondii PPi-PFK and increase accessibility to the intracellular parasite.

Molecular characterization of type I GABAA receptor complex from rat cerebral cortex and hippocampus

The molecular composition of the native gamma-aminobutyric acidA (GABAA) receptor complex is actually unknown. In the present communication we report a novel approach to characterize the minimal molecular conformation of the native GABAA receptor complex. This novel approach is based on the combination of subunit specific antibodies and specific 3H-labeled ligands in immunoprecipitation experiments. We have determined the presence of beta 2/3 and gamma 2 subunits in the Type I GABAA receptor complex, from rat cerebral cortex and hippocampus, by using two antibodies, the monoclonal 62-3G1 (specific for beta 2/3) and the polyclonal anti-gamma 2 (to the large intracellular loop of the gamma 2 short form) together with the Type I-specific ligand [3H]zolpidem. The association of gamma 2 and beta 2/3 subunits with the GABAA receptor complex was also tested using [3H]flumazenil. The results indicated that both gamma 2 and beta 2/3 were the most abundant subunits associated to either Type I or total benzodiazepine receptors from both cortex and hippocampus. Between 70-80% of Type I or total benzodiazepine binding activity was immunoprecipitated by either antibody. In addition, we have also investigated the coexistence of both subunits as part of the same population of Type I GABAA receptor complex by cross-immunoprecipitation experiments with 62-3G1 and anti-gamma 2. The results indicated that, in cerebral cortex, both gamma 2 and beta 2/3 subunits were part of the same population of Type I receptors. In hippocampus, an additional 20% of Type I receptors displayed either gamma 2 or beta 2/3 but not both subunits.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of beta interferon in resistance to Toxoplasma gondii infection

The role of recombinant murine beta interferon (rMuIFN-beta) and recombinant human IFN-beta (rHuIFN-beta) in resistance to Toxoplasma gondii was examined. rMuIFN-beta protected mice against a lethal infection with the parasite. The protective effect appeared to depend on the concomitant release of gamma interferon. rMuIFN-beta did not activate murine peritoneal macrophages to inhibit or kill T. gondii whether used alone or in combination with lipopolysaccharide (LPS). rHuIFN-beta did not activate human monocyte-derived macrophages to inhibit or kill T. gondii when 5-day-old monocyte-derived macrophages were used. In contrast, significant killing of T. gondii was noted when 10-day-old monocyte-derived macrophages were used. The addition of LPS enhanced this effect. These results revealed a role for IFN-beta in the mechanisms of defense against T. gondii and suggest its potential use in the treatment of toxoplasmosis in humans.