Effects of MK-801 and Phenytoin on Flurothyl-Induced Seizures During Development

Summary We determined the effects of the N-methyl-Daspartate (NMDA) receptor blocker MK-801 (0.05, 0.1, and 0.5 mg/kg intraperitoneally, i.p.) and phenytoin (PHT, 5, 10, and 20 mg/kg i.p.) on flurothyl-induced clonic and tonic-clonic seizures in 9-, 1 5, 30-, and 60-day-old male rats. Both agents had seizure-, age-, and dose-specific effects. The highest dose of MK-801 was anticonvulsant against clonic flurothyl-induced seizures only in 9- and 60-day-old rats, but suppressed tonic-clonic seizures in all ages. The lowest dose of MK-801 (0.05 mg/kg) produced significant anticonvulsant effects only in 15 day old rats. PHT did not have any effect on clonic seizures throughout development. Both doses of PHT (10 and 20 mg/kg) were anticonvulsant against tonic-clonic seizures in adult rats but not in any other age group. The results indicate that NMDA receptors play an important role in tonic-clonic flurothyl-induced seizures throughout development (especially in 15-day-old rats) and that the anticonvulsant effects of PHT may vary at different stages of brain development.     

Age-Specific Effects of Baclofen on Pentylenetetrazol-Induced Seizures in Developing Rats

Summary: Purpose : To determine whether seizures have age-specific features, we studied the role of γ-aminobutyric acid, (GABAB) transmission in rats of various ages (9, 15, 30, and 60 postnatal days). Methods: We used a GABA, receptor agonist baclofen (2 or 5 mg/kg intraperitoneally, i.p.) and a GABA_B receptor antagonist CGP 35348 (100 or 600 mg/kg i.p.) in the pentylenetetrazol (PTZ)-induced model of clonic and tonic-clonic seizures (100 mg/kg subcutaneously, s.c.).
Results : Whereas baclofen was anticonvulsant and CGP 35348 proconvulsant in most animals, there were distinct age-related differences in the effectiveness of these drugs and the antagonist had some anticonvulsant activity in adults. Furthermore, the two drugs acting at GABA_B receptors had a different profile of action in clonic seizures as compared with tonic-clonic seizures.
Conclusions : The differences in the age-specific action of the GABA_B agonist and antagonist suggest that different GABA_B receptor subsets may mediate the drug effects. The results indicate that putative antiepileptic drugs (AEDs) must be tested during development because it may not be possible to extrapolate age-specific anticonvulsant effects from studies in adult animals.     

Escherichia coli Nissle 1917 distinctively modulates T-cell cycling and expansion via toll-like receptor 2 signaling

Although the probiotic Escherichia coli strain Nissle 1917 has been proven to be efficacious for the treatment of inflammatory bowel diseases, the underlying mechanisms of action still remain elusive. The aim of the present study was to analyze the effects of E. coli Nissle 1917 on cell cycling and apoptosis of peripheral blood and lamina propria T cells (PBT and LPT, respectively). Anti-CD3-stimulated PBT and LPT were treated with E. coli Nissle 1917-conditioned medium (E. coli Nissle 1917-CM) or heat-inactivated E. coli Nissle 1917. Cyclin B1, DNA content, and caspase 3 expression were measured by flow cytometry to assess cell cycle kinetics and apoptosis. Protein levels of several cell cycle and apoptosis modulators were determined by immunoblotting, and cytokine profiles were determined by cytometric bead array. E. coli Nissle 1917-CM inhibits cell cycling and expansion of peripheral blood but not mucosal T cells. Bacterial lipoproteins mimicked the effect of E. coli Nissle 1917-CM; in contrast, heat-inactivated E. coli Nissle 1917, lipopolysaccharide, or CpG DNA did not alter PBT cell cycling. E. coli Nissle 1917-CM decreased cyclin D2, B1, and retinoblastoma protein expression, contributing to the reduction of T-cell proliferation. E. coli Nissle 1917 significantly inhibited the expression of interleukin-2 (IL-2), tumor necrosis factor alpha, and gamma interferon but increased IL-10 production in PBT. Using Toll-like receptor 2 (TLR-2) knockout mice, we further demonstrate that the inhibition of PBT proliferation by E. coli Nissle 1917-CM is TLR-2 dependent. The differential reaction of circulating and tissue-bound T cells towards E. coli Nissle 1917 may explain the beneficial effect of E. coli Nissle 1917 in intestinal inflammation. E. coli Nissle 1917 may downregulate the expansion of newly recruited T cells into the mucosa and limit intestinal inflammation, while already activated tissue-bound T cells may eliminate deleterious antigens in order to maintain immunological homeostasis.     

Amygdala-prefrontal coupling depends on a genetic variation of the serotonin transporter

Major depression is conditionally linked to a polymorphism of the human serotonin transporter gene (SLC6A4). During the presentation of aversive, but not pleasant, pictures, healthy carriers of the SLC6A4 short (s) allele showed stronger activation of the amygdala on functional magnetic resonance imaging. s carriers also showed greater coupling between the amygdala and the ventromedial prefrontal cortex, which may contribute to the abnormally high activity in the amygdala and medial prefrontal cortex seen in major depression.     

Quality control guidelines for testing gram-negative control strains with polymyxin B and colistin (polymyxin E) by standardized methods

An eight-laboratory study addressed the urgent need for quality control (QC) ranges for susceptibility determination when testing colistin (polymyxin E) and polymyxin B, two polycationic peptide antimicrobial agents, against multidrug-resistant gram-negative bacilli. For Escherichia coli ATCC 25922l, the QC ranges were as follows: for colistin, 0.25 to 1 microg/ml (11 to 17 mm), and for polymyxin B, 0.25 to 2 microg/ml (13 to 19 mm). For Pseudomonas aeruginosa ATCC 27853, the QC ranges were as follows: for colistin, 0.25 to 2 microg/ml (11 to 17 mm), and for polymyxin B, 0.25 to 2 mug/ml (14 to 18 mm). More than 97% of all reported QC results were within these proposed ranges.     

Genomic fingerprinting of bacteriocin-producer strains of Staphylococcus aureus

Among 363 strains of Staphylococcus aureus, 21 were shown to produce bacteriocins (Bac), antimicrobial peptides with potential biotechnological applications. This collection includes strains which are either isolated from food, patients and healthy cattle, or are involved in subclinical bovine mastitis. From these 21 strains, 17 were shown to carry closely-related 8.0-kb Bac plasmids encoding bacteriocins either identical to or similar to aureocin A70, a bacteriocin able to inhibit strains of Listeria monocytogenes, a food-borne pathogen. Such findings prompted us to investigate the genetic relationships among these Bac+ strains. To obtain more discriminatory results, a combined analysis of AP-PCR, rep-PCR, and a modified PCR technique that we designated SD-PCR was employed. The 17 Bac+ strains harboring 8.0-kb Bac plasmids exhibited seven fingerprint patterns. One such genotype was composed of 8 out of the 11 strains associated with bovine mastitis, which suggests the prevalence of a clone of Bac+ strains involved in this animal infection carrying 8.0-kb Bac plasmids. Our data support the assumption that Bac+ strains of S. aureus carrying genetically related 8.0-kb Bac plasmids do not belong to a single clone. It seems, therefore, that 8.0-kb Bac plasmids have spread horizontally among different S. aureus strains. There also seems to be genetic diversity among the remaining Bac+ strains analyzed.     

Transgenic rat model of Huntington's disease

Huntington's disease (HD) is a late manifesting neurodegenerative disorder in humans caused by an expansion of a CAG trinucleotide repeat of more than 39 units in a gene of unknown function. Several mouse models have been reported which show rapid progression of a phenotype leading to death within 3-5 months (transgenic models) resembling the rare juvenile course of HD (Westphal variant) or which do not present with any symptoms (knock-in mice). Owing to the small size of the brain, mice are not suitable for repetitive in vivo imaging studies. Also, rapid progression of the disease in the transgenic models limits their usefulness for neurotransplantation. We therefore generated a rat model transgenic of HD, which carries a truncated huntingtin cDNA fragment with 51 CAG repeats under control of the native rat huntingtin promoter. This is the first transgenic rat model of a neurodegenerative disorder of the brain. These rats exhibit adult-onset neurological phenotypes with reduced anxiety, cognitive impairments, and slowly progressive motor dysfunction as well as typical histopathological alterations in the form of neuronal nuclear inclusions in the brain. As in HD patients, in vivo imaging demonstrates striatal shrinkage in magnetic resonance images and a reduced brain glucose metabolism in high-resolution fluor-deoxy-glucose positron emission tomography studies. This model allows longitudinal in vivo imaging studies and is therefore ideally suited for the evaluation of novel therapeutic approaches such as neurotransplantation.     

The efficacy of montelukast in the treatment of cat allergen-induced asthma in children

BACKGROUND: Montelukast is a leukotriene antagonist approved for the treatment of childhood asthma in children age 2 years and older. There are limited studies on its effects on allergic asthma in children. OBJECTIVE: We sought to evaluate montelukast's effects on upper and lower airway responses to intense cat allergen exposure. METHODS: In a double-blind, placebo-controlled, cross-over trial 18 subjects aged 6 to 14 years with cat-induced asthma were randomly assigned to receive 1 week each of either montelukast or placebo, followed by a 1-hour cat challenge in an environmental exposure unit. Upper and lower respiratory tract symptoms were rated, and spirometry and acoustic rhinometry were performed. Challenges were stopped early if the subject became too uncomfortable or had a greater than 50% decrease in FEV1. RESULTS: Overall changes in FEV1 were significantly different with montelukast treatment and remained significant after adjusting for allergen level (P =.02; adjusted P =.01). Lower respiratory tract symptom scores were significantly reduced with montelukast versus placebo (P =.007) but lost significance after adjusting for allergen level (P =.16). Challenge length was significantly longer with montelukast versus placebo (P <.001) and remained significant after adjusting for allergen level (P =.019). Montelukast did not significantly affect upper respiratory responses, as measured by means of symptom scores (P =.43) and changes in acoustic rhinometry (P =.078). CONCLUSIONS: Montelukast was significantly more effective than placebo in attenuating lower respiratory responses and extending challenge length when cat-sensitive children with mild persistent asthma were exposed to high levels of cat allergen.     

Partial purification and characterization of anhydrotetracycline oxygenase of Streptomyces aureofaciens

Anhydrotetracycline oxygenase was purified both by affinity chromatography and by hydrophobic interaction chromatography. Molecular weight of anhydrotetracycline oxygenase was determined to be 115,000 by Sephadex G-200 gel filtration. Using preparative isoelectric focusing the isoelectric point of the enzyme was estimated to be 5.3. The enzyme showed a sensitivity to thiol-specific inhibitors. During the hydrophobic interaction purification step, the activity dropped considerably. Reactivation occurred when a heat treated crude extract was added to the reaction mixture.     

Desensitization to substance P following intrathecal injection

Summary The intrathecal injection of substance P (SP) (2.5–15 g) has been shown to produce hyperalgesia in the rat tail flick test. Repeated injection of SP (7.5 or 15 g) or pretreatment with two of these doses produces desensitization to this hyperalgesic response. Desensitization is doserelated with respect to degree and duration. This phenomenon is relatively specific because the hyperalgesic response to methysergide, a serotonin receptor antagonist, is unaffected, while that produced by phentolamine, an adrenergic receptor antagonist, is much less affected than that of SP. Pretreatment with a desensitizing regimen of SP potentiates the antinociceptive effect of morphine and baclofen when they are tested immediately after the regimen but if a 30 min delay is permitted, an inhibition of their effects is observed. These results support the notion that the spinal antinociceptive effect of morphine and baclofen is due to an interaction with SP mechanisms in the spinal cord, the nature of which may be more complex than is presently understood. Desensitization produces no change in baseline responsiveness in the tail flick test. This suggests that the hyperalgesic response to SP is due either to an action at a site other than the primary afferent synapse, or if it is at this site either compensatory mechanisms occur or SP is not the primary determinant of tail flick latency but may play a modulatory role.