Central auditory processing, MRI morphometry and brain laterality: applications to dyslexia

We review data from our laboratory related to a view of dyslexia as a biological disorder, or deficit, caused by both structural and functional brain abnormalities. The review is focused on central auditory processing in dyslexia, and the possibility that impairments in the auditory or acoustic features of the phonological code may be at the heart of the impairments seen in dyslexia. Three methodological approaches by which to investigate central auditory processing deficits are outlined: dichotic listening (DL) to consonant-vowel syllables; magnetic resonance imaging (MRI), and the use of event-related potentials (ERPs). Consonant-vowel syllable DL is a technique for probing the functional status of phonological processing areas in the superior temporal gyrus, particularly in the left hemisphere. MRI is a corresponding structural, or morphological, measure of anatomical abnormalities in the same brain region, particularly covering the planum temporale area. The ERP technique, and particularly the mismatch negativity (MMN) component, reveals cortical dysfunctions in sensory processing and memory related to basic acoustic events. For all three approaches, the dyslexic children were seen to differ from their control counterparts, including absence of modulation of the right ear advantage (REA), in DL through shifting of attention, smaller left-sided planum temporale asymmetry, and prolonged latency in the MMN ERP complex, particularly in the time-deviant stimulus condition.

Spin concentration in a possible ESR dosimeter: An electron spin echo study on X-irradiated ammonium tartrate

Several single crystals and powder samples of ammonium tartrate, recently proposed as a possible ESR dosimeter, have been X-irradiated with different doses. The total radical concentration has been determined by quantitative cw ESR, by comparison with a standard. The samples have been studied by electron spin echo spectroscopy. The two-pulse echo decay has been obtained and simulated by a single exponential function for different values of the microwave power of the pulses and for different pulse lengths. The dependence of the phase memory time TM on the microwave power has been exploited to get information on the contribution of the instantaneous diffusion to spin dephasing. At room temperature in the range of radical concentrations of 10(18)-10(19) spins/cm3 the instantaneous diffusion is the dominant spin dephasing mechanism. The linear dependence of the instantaneous diffusion on the total concentration of the radicals is in agreement with the theory. From the latter result we conclude that the average radical-radical distance corresponds to a random distribution of the radicals in the matrix. A simple method of measuring the radical concentration by the ESE decays in powder samples of irradiated ammonium tartrate is described.

Purification and characterisation of a tissue specific elongation factor 1 alpha (EF-1 alpha 2) from rabbit muscle

The peptide elongation factor 1 alpha (EF-1 alpha) has been isolated and characterised from a number of species. Recently we and others have reported the existence of an isoform of the ubiquitously expressed EF-1 alpha mRNA in higher eukaryotes, including human cells. This isoform has a tissue specific expression pattern, confining it primarily to muscle, heart, and brain. In the present study we have purified the isoform of EF-1 alpha from rabbit muscle. Using partial amino acid analysis, we can conclude that in rabbit muscle essentially only the isoform of elongation factor 1 alpha, designated EF-1 alpha 2, is translated. Preliminary activity assays show that the isoform has the same functional activities as the normal EF-1 alpha, designated EF-1 alpha 1, in relation to protein synthesis, but may behave differently in the ability to bind nucleotides. Based on the availability of the isoforms of EF-1 alpha purified from a mammalian species, it will be possible to conduct further comparative studies in order to elucidate the different functions of EF-1 alpha 1 and EF-1 alpha 2 proteins.

The elongation factor 1 A-2 isoform from rabbit: cloning of the cDNA and characterization of the protein

Eukaryotic elongation factor 1 A (eEF1A, formerly elongation factor-1 alpha) is an important component of the protein synthesis apparatus. Here we report the isolation and characterization of the cDNA sequence encoding rabbit eEF1A-2, an isoform of eEF1A, as well as a structural and functional comparison of the two rabbit isoforms. Northern analysis of the expression pattern of eEF1A-2 showed that this isoform is expressed in skeletal muscle, heart, brain and aorta, while transcripts are not detected in liver, kidney, spleen and lung. In contrast, the previously characterized eEF1A-1 isoform is expressed in all tissues examined except skeletal muscle. We have recently purified eEF1A-2 from rabbit skeletal muscle. By partial amino acid sequencing and determination of the post-translational modifications of eEF1A-2 we found that both of the glycerylphosphorylethanolamine modifications observed in eEF1A-1 appear to be present in eEF1A-2. However, two of the residues found dimethylated in eEF1A-1 appeared to be trimethylated in eEF1A-2. A comparison of the enzymatic activity showed that eEF1A-1 and eEF1A-2 have indistinguishable activity in an in vitro translation system. In contrast, the GDP dissociation rate constant is approximately 7 times higher for eEF1A-1 than for eEF1A-2. The nucleotide preference ratio (GDP/GTP) for eEF1A-1 was 0.82, while the preference ratio for eEF1A-2 was 1.50.

Metabolic fingerprinting and fermentative capacity of the intestinal flora of pigs during pre- and post-weaning periods

We used the Phene Plate generalized microplates to investigate the metabolic activities of faecal flora of pigs during pre- and post-weaning periods. Weekly samples were collected from four sows and their litters (four piglets from each) during 5 months. The metabolic fingerprints obtained from faecal floras of sows and their litters in the first sampling occasion was very similar, suggesting that sows were the initial source of flora for piglets. This similarity, however, was lost in week 2 and piglets developed new types of flora which, although similar among the litter-mates, differed from those of the sows. The metabolic fingerprints of pigs' floras during the post-weaning period also differed from those of the suckling period. On day 70 pigs were transferred to a fattening stable. The faecal flora of the animals during this period was unstable in each individual and differed among litter-mates. A pattern of successive changes was observed in the fermentative capacity (FC) of pigs' floras reaching the highest value before weaning (day 34). An overall decrease in the FC value of faecal floras was observed as a consequence of dietary shifts from milk to solid food to high energy fattening diet. The mean FC value of pig floras on the first sampling occasion (mean +/- S.D. = 0.41 +/- 0.02) was significantly higher than that obtained in the last sampling occasion (day 145) (0.31 +/- 0.04) (P < 0.001). Faecal floras of sows also had lower FC values (0.25 +/- 0.01) than those of piglets suggesting that loss of FC by the faecal flora of young pigs will continue as they age.

Assignment of human elongation factor 1alpha genes: EEF1A maps to chromosome 6q14 and EEF1A2 to 20q13.3

The human elongation factor 1alpha gene family consists of at least 2 actively transcribed genes, EEF1A and EEF1A2, and more than 18 homologous loci. EEF1A2 is expressed in a tissue-specific manner, whereas EEF1A is expressed ubiquitously, and both of them can function in translation. An EEF1A cDNA probe has previously been shown to cross-hybridize with several human chromosomes, but the location of the functional gene has not been established. We have mapped the functional EEF1A gene to 6q14 by combined fluorescence in situ hybridization (FISH) and PCR analysis of a somatic cell hybrid panel and mapped EEF1A2 to 20q13.3 by FISH. In addition, the 11 strongest cross-hybridizing loci (EEF1AL2-EEF1AL13) were mapped by FISH to 12p12, 9q34, 7p15-p21, 19q13, 3q26-q27, 7q33-q35, 1p13-p22, 2q12-q14, 5p12-q11, 1q31-q32, and Xq21.

Immunoprophylaxis of bovine dermatophytosis

The literature on immunoprophylaxis as control method for ringworm in cattle is reviewed. Scientific papers on immune response to dermatophyte antigens and vaccination against ringworm were obtained from personal files and computerized search in 4 relevant databases. Vaccines with antigens of Trichophyton verrucosum stimulate a humoral and cellular immune response. In animals vaccinated with inactivated vaccines, some protection is observed after challenge. However, the protective immunity is inadequate in most cases. Vaccination with live vaccines elicits an immune response that prevents the development of clinical disease. The protective immunity is based mainly on the cellular branch of the immune system. The efficacy and safety of live dermatophyte vaccines have been demonstrated in both challenge experiments and field trials from different countries. Effective control of ringworm in cattle has been achieved in regions implementing systematic vaccination.

Phenotypic characterization of intestinal Escherichia coli of pigs during suckling, postweaning, and fattening periods

A highly discriminatory and standardized biochemical fingerprinting method was used to monitor the persistence and colonization of intestinal Escherichia coli isolated from the feces of four sows and their litters (four piglets from each) during the suckling, postweaning, and fattening periods. Altogether, 195 fecal samples were collected and 1,827 E. coli strains were tested (mean number of isolates tested per fecal sample per pig, 9.5). Strains were divided into similarity groups on the basis of their biochemical phenotypes (BPTs). The diversity of E. coli strains in each sample was measured with Simpson's index of diversity, and similarity between E. coli floras of piglets was calculated with a population similarity index. Each fecal sample contained several BPTs of E. coli, some of which dominated that population. The intestinal colonization of piglets consisted of successive waves of different E. coli BPTs, the tenure of which varied from a few days to 2 weeks. Most of these BPTs disappeared in the succeeding samples and were not recovered again from the same piglets. On the other hand, some E. coli strains which colonized piglets early during the suckling period persisted for a long period and were referred to as resident BPTs. Each piglet carried more than one resident BPT (mean of 2.4 BPTs per pig), some of which were also found in other piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

Different functions of spinal 5-HT1A and 5-HT2 receptor subtypes in modulating behaviour induced by excitatory amino acid receptor agonists in mice

The modulating effects of 5-HT1A and 5-HT2 receptor agonists on behaviour spinal excitatory amino acid (EAA) agonists were examined. Intrathecal (i.th.) administration of both N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) produce a behavioural syndrome of caudally directed biting and scratching. Serotonin (5-HT) agonists were coadministered with either NMDA or AMPA, and changes in EAA-induced behaviour were scored. All drugs were administered i.th. The 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT) (15-60 nmol) reduced both NMDA (0.25 nmol) and AMPA (0.06 nmol) induced behaviour in a dose-dependent manner, and preadministration of the 5-HT1A receptor antagonist, 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine hydrobromide (NAN-190) (20 nmol) reversed this effect. The administration of the 5-HT2 agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.7-28 nmol) produced a dose-dependent behavioural syndrome similar to the EAA agonists. This was reversed by preadministration of ritanserin (10 nmol), a 5-HT2 antagonist. When DOI was coadministered with NMDA (0.25 nmol) or MAPA (0.06 nmol) there was an increase in the behaviour recorded and this effect was antagonised by ritanserin. The results of this study implicate that in the spinal cord subtypes of 5-HT receptors have different effects on modulation of behaviour induced by activation of the NMDA or the AMPA receptors; the activated 5-HT1A receptors have an inhibitory effect whereas activation of the 5-HT2 receptors enhance the induced behaviour.

Chronic, combined treatment with desipramine and mianserin: enhanced 5-HT1A receptor function and altered 5-HT1A/5-HT2 receptor interaction in rats

A greater percentage of depressed patients respond to combined treatment with a tricyclic antidepressant and the tetracyclic antidepressant mianserin than to treatment with these drugs given alone. The functional sensitivity of the 5-hydroxytryptamine (5-HT)1A receptor, and the functional interaction between the 5-HT1A and the 5-HT2 receptors were investigated after treatment with desipramine and mianserin either alone or combined for 21-28 days. Pretreatment with desipramine and mianserin in combination induced the most intense 5-HT syndrome and the greatest fall in colonic temperature after injection of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT). The rats pretreated with desipramine alone had the largest elevation of the response temperature in the increasing temperature hot-plate test after injection of 8-OH-DPAT. After the combined pretreatment with desipramine and mianserin, no enhanced functional response in these tests was found when the 5-HT1A and the 5-HT2 receptors were stimulated simultaneously using 8-OH-DPAT and the 5-HT2 agonist, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI), contrasting the findings for desipramine or mianserin treatments given alone, where an increased functional response was found for the colonic temperature and the response temperature in the increasing temperature hot-plate test. In vitro receptor binding using [3H]-8-OH-DPAT as ligand revealed an increase in Kd and Bmax in the spinal cord after chronic treatment with the combination of desipramine and mianserin. In the hippocampus and the frontal cortex the changes were small.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of NMDA-induced behaviour after acute and chronic administration of desipramine in mice

The mechanisms of the antinociceptive effect of desipramine (DMI) are only partly known. It is generally accepted that excitatory amino acids act as neurotransmitters in primary nociceptive fibres and recent in vitro studies have shown an interaction between tricyclic antidepressants and the N-methyl-D-aspartic acid (NMDA) receptor complex. In this study, the modulatory effect of DMI on the biting and scratching behaviour induced by intrathecal (i.th.) administration of NMDA (0.25 nmol) was investigated. Desipramine was administered acutely, either intrathecally (0.7-35 micrograms) or intraperitoneally (i.p., 10 mg/kg), or chronically in the drinking water (0.15 g/l) for 3 weeks. The NMDA-induced behaviour was significantly reduced both after acute and chronic administration of DMI. Several studies have shown a functional upregulation of the 5-HT1A receptor after chronic treatment with DMI. The activation of this receptor using the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT), leads to a reduction in NMDA-induced behaviour. Using the 5-HT1A antagonist NAN-190 (10 micrograms, i.th.), the effect of chronic administration of DMI on the NMDA-induced behaviour was reversed. However, NAN-190 also increased NMDA-induced behaviour in the control group, suggesting that a tonic inhibition of this behaviour, mediated by the 5-HT1A receptor, may exist. These findings indicate that DMI may reduce glutaminergic transmission at the spinal NMDA receptor. As this receptor is central in spinal nociceptive transmission, this could be one mechanism for the antinociceptive effect of DMI.

Antinociceptive effects of intrathecal administration of alpha-adrenoceptor antagonists and clonidine in the formalin test in the mouse

The hypothesis that the descending noradrenergic system tonically inhibits nociception at the spinal level was investigated, using the formalin test in mice. The alpha-adrenoceptor agonist clonidine (0.46 and 0.92 microgram), injected intrathecally, significantly reduced licking activity in both the early and late phase of the test. The alpha 1-antagonist prazosin (3.75, 7.5 and 15 micrograms) and the alpha 2-antagonist yohimbine (7.5 micrograms) also significantly reduced licking activity in both phases. The smaller doses of yohimbine (1.87 and 3.75 micrograms) induced an insignificant reduction of licking in the early phase. Except for the largest doses of clonidine (0.92 microgram), the drugs used had no effect on the general level of activity and motor performance. These results support previous findings that increased noradrenergic activity in the spinal cord inhibits nociception, however, this inhibition seems not to be tonically active. The mechanisms of the antinociceptive actions of alpha-antagonists are not clear.

The role of 5-HT1A and 5-HT1B receptors in spinal nociceptive transmission and in the modulation of NMDA induced behaviour

The effects on nociception of intrathecal (i.th.) administration of selective 5-HT1A and 5-HT1B agonists were studied in rats. Nociception was evaluated using the tail-flick test with adjustments for tail-skin temperature, the increasing temperature hot-plate test and the scoring of biting and scratching behaviour after i.th. N-methyl-D-aspartate (NMDA). Activation of the spinal 5-HT1A receptor induced an antinociceptive effect in the increasing temperature hot-plate test and produced a dose dependent decrease in NMDA-receptor mediated behaviour. No significant change in nociception measured by either of the nociceptive tests was found after administration of the 5-HT1B agonist. These results support the hypothesis that spinal 5-HT1A receptor activation has an antinociceptive effect, and indicate a possible interaction between the serotonergic and glutaminergic transmitter systems.

In vitro solubility of human pulp tissue in calcium hydroxide and sodium hypochlorite

The tissue solvent capacity of a 2% stabilized sodium hypochlorite solution (Milton) and a commercial calcium hydroxide solution (Calasept) was examined under in vitro conditions where autolyzed human pulp fragments weighing approximately 0.0065 g were immersed in these solutions at 37 degrees C for periods of up to 10 days. It appeared that sodium hypochlorite was able to dissolve half the volume of pulp tissue within 1 h and the remaining tissue after 2-2 1/2 h. Calcium hydroxide dissolved half the pulp volume within 2 h, whereas it took 1 week for the remaining tissue to dissolve. These findings support the use of sodium hypochlorite as an irrigation solution during canal preparation and calcium hydroxide as a canal dressing for the purpose of creating a canal free of pulp remnants before root filling.

Characterization of Escherichia coli strains isolated from pigs with edema disease

Escherichia coli strains belonging to serogroups O 138 and O 139 isolated from pigs with edema disease, were characterized with respect to the presence of genes encoding Shiga-like toxin I, Shiga-like toxin II and Shiga-like toxin IIv (SLT I, SLT II and SLT IIv). Genes coding for the heat-stable and heat-labile enterotoxins (ST I and LT I) were also detected. Plasmid profiling, restriction enzyme digestion of total DNA, and ribotyping were performed for further characterization of the strains. The oligonucleotide probes applied in this study appeared to be useful tools for detecting genes coding cytotoxins and enterotoxins. DNA from 12 of 16 strains hybridized with two SLT II probes, and DNA from two SLT IIv encoding strains also hybridized with the ST I probe. DNA from one SLT IIv negative strain hybridized with the LT I probe. The results from plasmid profiling, restriction enzyme digestion, and ribotyping were compared with serogrouping in attempts to distinguish between the different E. coli edema disease isolates. Fourteen different plasmid profiles were identified, and as restriction patterns barely did, and ribotyping patterns did not, reveal any information useful for differentiation of the strains beyond serogroup level, plasmid profiling seemed to be the most suitable method for discrimination between the edema disease strains investigated here.

Desipramine, administered chronically, influences 5-hydroxytryptamine1A-receptors, as measured by behavioral tests and receptor binding in rats

The 5-hydroxytryptamine1A (5-HT1A) receptor subtype seems to be of importance in the pathogenesis of depression and in the mode of action of antidepressants. In this study, behavioural experiments were performed in rats after oral administration of desipramine for 18-20 days, followed by an acute injection of the selective 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), either systemically or intrathecally. Chronic administration of desipramine prolonged the behavioural 5-HT syndrome in the animals injected systemically with 8-OH-DPAT. Treatment with desipramine was also found to potentiate and prolong the antinociceptive effect of an acute injection, systemically or intrathecally, of 8-OH-DPAT in the increasing temperature hot plate test. After systemic administration of 8-OH-DPAT, the colonic temperature was lowered similarly in the desipramine-treated group and in controls, whereas an intrathecal injection of 8-OH-DPAT resulted in a fall in the colonic temperature in the desipramine-treated group only. In vitro receptor binding studies, using [3H]8-OH-DPAT as the ligand, showed a statistically significant reduction of Kd and Bmax in the frontal cortex and of Kd in the spinal cord, after treatment with desipramine. No changes of Kd and Bmax were found in the hippocampus after this treatment. Thus, desipramine, administered chronically, resulted in a functional up-regulation of the 5-HT1A-receptors, both spinally and supraspinally, whereas in the in vitro receptor binding, a slight down-regulation or no change was found. It seems therefore that the results of in vitro receptor binding studies do not necessarily reflect the functional state of the neuronal system.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of the gene encoding EF-1 alpha O, an elongation factor 1-alpha expressed during early development of Xenopus laevis

In Xenopus laevis, the gene encoding the elongation factor 1-alpha variant EF-1 alpha O, where O stands for oocyte, is expressed in oocytes and early embryos. A genomic library from X. laevis was screened with a cDNA probe coding for EF-1 alpha O. Two recombinant phages were isolated, one of which carries an entire EF-1 alpha O gene. This clone was characterized by restriction enzyme mapping and sequencing. Comparison of cDNA and genomic sequences revealed that EF-1 alpha O consists of seven exons spanning about 6.5 kb. The structure of the gene is very homologous to the human EF-1 alpha gene, as all locations of the splice junctions are conserved between the two genes. The sequence immediately upstream from the transcription start point (tsp) contains a CCAAT box, but does not contain either a TATA box or a Sp1-binding site. Interestingly, this sequence has a sequence homologous to the negative regulatory element from the TFIIIA promoter. A region located about 400 bp upstream from the tsp contains an additional number of possible regulatory sequence elements. The first intron contains G + C-rich elements which exist both isolated and as part of longer inverted repeats. Furthermore, one octamer and four Sp1-binding sites are found in this intron.

Electron trapping and reactions in rhamnose by ESR and ENDOR

The main objective for a reinvestigation of rhamnose was to devise a mechanistic link between the trapped electron detected previously and the secondary radicals observed at 77 K and at room temperature. Single crystals of rhamnose were X-irradiated at temperatures between 15 and 300 K and examined using ESR, ENDOR, and field-swept ENDOR techniques. After low-temperature irradiation a C3 H-abstraction radical is formed following the visible light-induced decay of the trapped electron. This species was previously assigned erroneously to a C2 H-abstraction species. At temperatures above 120 K, this radical deprotonates at the C3 hydroxy group. Furthermore, a C2 H-abstraction radical is formed following the thermally induced decay of the trapped electron. The C2 and C3 H-abstraction radicals did not convert into each other. A third radical species formed at low temperatures is a C5 H-abstraction radical. It is unstable above 250 K and decays without any apparent successor. The C2 and C3 H-abstraction radicals are formed thermally and photochemically from the parent trapped electron. The conversions are mediated by hydrogen atoms formed intermediately or by elimination of hydride ions. The thermal decomposition pathway requires further studies, in particular with respect to the possible role of water. Recently, Box et al. analyzed the site of the trapped electron in rhamnose crystals. The present results support the results obtained by these authors (Radiat. Res. 121, 262 (1990)). In particular, trapped electron vs proton distances closely match the conversion mechanisms suggested.

A nested PCR followed by magnetic separation of amplified fragments for detection of Escherichia coli Shiga-like toxin genes

The Shiga-like toxin (SLT) I and II genes in cytotoxic Escherichia coli strains were detected using a polymerase chain reaction (PCR) procedure. Identification and differentiation of SLT I and II was carried out using primers giving PCR-generated DNA fragments of different size for the two cytotoxins. A two-step PCR procedure utilizing three primers in a nested configuration for both SLT I and II was combined with magnetic separation to identify the toxin genes in a rapid, specific and sensitive test system designated DIANA (Detection of Immobilized Amplified Nucleic Acid). The first PCR was carried out using standard methods, and the product generated was used as primer in the second PCR. In this procedure one of the primers from the first PCR was used with biotin label, and the second (inner) primer was 32P-labelled. The double-stranded DNA fragments generated containing the two primers, were biotinylated on one 5' end and 32P-labelled on the other 5' end. These fragments were separated from the solution using streptavidin-coated super-paramagnetic microscopic beads. The test could detect and differentiate between SLT I and II in a positive/negative ratio of more than 20. The assay could detect five SLT-positive E. coli organisms in the 5 microliters test sample. The presence of 100-fold more SLT-negative strains in a sample did not adversely affect the test signal.

Potentiation of a behavioural response in mice by spinal coadministration of substance P and excitatory amino acid agonists

The functional interaction in the spinal cord between substance P and excitatory amino acid agonists was investigated. Behavioural responses were scored in mice after intrathecal administration of excitatory amino acid agonists and substance P, given separately or in combination. A strong potentiation of the effect was seen when substance P was coadministered with N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) or kainic acid (KA). The potentiation was blocked by the corresponding antagonists: the selective NMDA-receptor antagonist (+/-)-3- (2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP), the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and the substance P analog, [D-Arg1,D-Trp7,9,Leu11]-substance P (Spantide). These findings indicate a functional interaction between substance P and glutamate in the dorsal horn of the spinal cord, compatible with the hypothesis that corelease of substance P and glutamate from primary afferent neurons may enhance nociception.

The behavioural response to intrathecal serotonin is changed by acute but not by repeated treatment with zimelidine or metergoline

The behavioural response to intrathecal serotonin (5-HT) was examined in mice after acute and after withdrawal of repeated treatment with the 5-HT uptake inhibitor zimelidine or the 5-HT receptor antagonist metergoline. Intrathecal 5-HT elicits a response consisting of biting or licking of the lower part of abdomen and reciprocal hindlimb scratching, indicative of nociceptive stimulation. Acute injection of zimelidine (20 mg/kg) significantly increased the response to intrathecal 5-HT (0.25-1 micrograms) whereas a single dose of metergoline (5 mg/kg) completely blocked the response to intrathecal 5-HT (2 micrograms). The behavioural response to intrathecal 5-HT (0.25-2 micrograms) was not significantly changed 48 hr after withdrawal of repeated treatment with zimelidine (2 x 10 mg/kg/day for 14 days) or metergoline (2 x 2.5 mg/kg/day for 14 days). In the present experiments acute zimelidine appeared to increase nociceptive responsiveness, whereas metergoline had the opposite effect. This study does not provide evidence that long-term treatment with zimelidine or metergoline leads to adaptive changes in the response to spinal cord 5-HT receptor stimulation.

Inhibition by glutamate antagonists, MK-801 and NBQX, of cutaneo-cardiovascular pain reflex in rats

In urethane-anesthetized rats, xylene applied locally to the skin of the hind paws was shown to induce reflex increases of blood pressure (33%) and heart rate (37%). The blood pressure elevation was dose dependently inhibited by the NMDA antagonist, MK-801 (0.3-1.0 mg/kg i.v.), and by the AMPA (D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxalonepropionic acid) antagonist, NBQX (2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline 0.1-1.0 mg/kg per min). In contrast, only the latter compound was shown to block dose dependently the observed increase in heart rate. The results suggest that the two glutamate antagonists inhibit nociceptive impulse traffic at distinct anatomical sites and/or by different modes of actions.

Immunomagnetic separation and DNA hybridization for detection of enterotoxigenic Escherichia coli in a piglet model

Enterotoxigenic Escherichia coli (ETEC) strains were detected by stool blot hybridization assays using different oligonucleotide probes for the colonization fimbrial antigen F4, heat-stable enterotoxin I (ST I), and heat-labile enterotoxin (LT I) genes. Forty-eight fecal samples and seven samples of intestinal content from ETEC-challenged newborn piglets were processed in two ways: (i) by direct inoculation of bacterial suspension onto nylon membranes overlaying blood agar and (ii) by immunomagnetic enrichment of F4+ ETEC using magnetic beads coated with F4 monoclonal antibodies before inoculation onto nylon membranes. In samples obtained from nondiarrheic piglets pre- and postchallenge, E. coli genes for F4, ST I, and LT I could be detected only after immunomagnetic enrichment. No difference between the two methods in detection of these E. coli genes was observed when stool blots from diarrheic piglets were examined. By using magnetic separation, it was easy to decrease background bacterial flora, intestinal cells, and fecal debris and thus produce purer specimens. The method evaluated in this animal model appeared simple and quick and increased the sensitivity of detection of ETEC strains 100-fold compared with the direct stool blot hybridization assays. Prior bacterial isolation and identification were not necessary.

Chronic administration of desipramine and zimelidine changes the behavioural response in the formalin test in rats

In studies of the effect on nociception of chronic administration of antidepressants, the stress of the injections may influence the results. In this experiment, desipramine or zimelidine were administered in the drinking water of rats, in a concentration yielding a dose of approximately 8 mg/kg/24 hr. Desipramine, given both for a short time (24 hr) and chronically (14 days), induced antinociception in the increasing temperature hot-plate test; zimelidine did not significantly influence the results of this test. In the tail-flick test, neither short-term nor chronic administration of these antidepressants had any effect on nociception, when correction was made for the changes in the temperature of the tail skin. In the formalin test, nine behavioural categories were scored for 1 hr and the data were treated statistically, using a multivariate analysis. Chronic administration of desipramine increased nociceptive behaviour during the first 10 min of the test. Desipramine and, to a lesser extent, zimelidine, changed the response in the late phase (10-60 min), showing less focussed pain-related behaviour (jerks and shaking, licking and biting of the injected paw) and more non-focussed pain-related behaviour (activity states with elevation or protection of the injected paw). It was concluded that desipramine is antinociceptive in the increasing temperature hot-plate test. Desipramine and zimelidine, administered chronically, modify the late phase of the formalin test towards less focussed pain-related behaviour, suggesting an antinociceptive effect. Multivariate analysis of the data of the formalin test seemed to be of value for the interpretation of the data.

Antinociceptive effect of paracetamol in rats is partly dependent on spinal serotonergic systems

The possible involvement of bulbo-spinal monoaminergic pathways in the antinociceptive effect of paracetamol was investigated in rats. Serotonergic pathways were lesioned with intrathecal 5,6-dihydroxytryptamine (5,6-DHT), and noradrenergic pathways with 6-hydroxydopamine (6-OHDA). Intact and lesioned rats were tested in the formalin test after i.p. paracetamol (400 mg/kg) or vehicle. Behaviour was scored for 1 h after the dorsal injection of 100 microliters of 5% formalin into one hind paw. Behavioural variables were evaluated with a multivariate statistical procedure, as well as an analysis of variance. Paracetamol itself reduced pain-related behaviour and increased normal motor activity. This antinociceptive effect was reduced in rats lesioned with 5,6-DHT. In lesioned rats paracetamol caused a change in nociceptive behaviour from active, focused behaviour towards passive, protective and non-focused behaviour in the early phase of the formalin test. No significant effect of lesioning with 6-OHDA upon the paracetamol effect was found. These results show that activation of spinal serotonergic systems is involved in the antinociceptive effect of paracetamol. The relative importance of this mechanism in the central effect of paracetamol and the mechanisms that cause the activation remain to be determined.

Pathogenic Escherichia coli found in food

The bacteria constituting the species Escherichia coli are commonly found in the intestinal flora of man and animals, and were until late 1950s recognized as non-pathogenic normal cohabitants. However, certain strains might induce disease, and E. coli should therefore be regarded as a potential pathogenic organism. The pathogenic strains can cause distinct disease syndrome as different diarrheal diseases, wound infections, meningitis, septicemia, artherosclerosis, hemolytic uremic syndrome and immunological diseases such as reactive and rheumatoid arthritis. Several different groups of diarrhea-inducing strains are known. The enterotoxigenic E. coli (ETEC) strains produce one or more of toxins from the heat-labile and the heat-stable enterotoxin families. These strains possess specific adhesion fimbria for intestinal attachment and colonization. Some enteropathogenic E. coli strains (EPEC) produce one or more of the cytotoxins, but adhere also to intestinal cells interfering with the electrolyte transport system. The group of strains possessing invasive properties are designated enteroinvasive E. coli (EIEC). Recently, the enterohemorrhagic E. coli (EHEC) strains have been identified and shown to produce one or more of the cytotoxins (vero-cytotoxins, shiga-like toxins). Food originating from warm-blooded animals may be contaminated with E. coli, but contamination from human sources are more common for food involved in outbreak of disease. In general, strains causing disease in animals do possess other colonization factors than those found on human pathogenic strains. EIEC strains are, like Shigella, only known to induce disease in man. However, both healthy and sick cattle are suspected to be a major reservoir for EHEC strains, and several outbreaks have been associated with consumption of meat or meat products. Cheeses have been the source of outbreaks of both ETEC and EIEC in Europe and the USA, while water seems to be a major source for the different diarrheic E. coli strains affecting children and tourists in the 3rd world. Strains causing non-enteric disease are less known as being transmitted to humans with food as a vector, but the importance of some of these diseases, should implicate further research on what role food plays in spreading these organisms. The recipient of the potential pathogenic E. coli through food, the humans, are also of different risk of contracting diseases.(ABSTRACT TRUNCATED AT 400 WORDS)

Antinociceptive effect of intrathecally-administered desipramine and zimelidine in rats

The effect of intrathecally (i.th.) administered desipramine and zimelidine, in doses of 5, 10 and 50 micrograms, were investigated in the tail-flick test with simultaneous measurement of the temperature of the tail skin and in the increasing temperature hot-plate test. A constant negative correlation between the temperature of the tail skin and tail-flick latency, as described previously, was found. For all doses tested, desipramine induced longer tail-flick latencies, 10 min after injection than vehicle and the temperature of the tail skin tended to increase less in this group than in controls. After adjustment of the tail-flick latencies for the changes in the temperature of the tail skin, an antinociceptive effect of desipramine was still found. For zimelidine, only the largest dose (50 micrograms) was found to be antinociceptive, after adjustment for the tail skin temperature. In the increasing temperature hot-plate test, no antinociceptive effect of these antidepressants was found. For desipramine and zimelidine, the effect in the tail-flick test, 10 min after injection, indicates that the antinociceptive effect of these drugs may have, at least partly, a spinal site of action. In the increasing temperature hot-plate test, the response is integrated supraspinally. This may partly explain the lack of effect in this test when desipramine and zimelidine were administered intrathecally.

Teat lesions with reference to housing and milking management

Potential associations between teat lesions and housing, hoof care, milking machine and milking management, were investigated. Overmilking, pulsation ratios of 71%, height of manger edge in the short type of stalls, and insufficient hoof care were associated with an increased incidence of teat lesions. The associations of pulsation ratio and overmilking suggest that factors disposing for teat end oedema and/or irritation during milking might cause teat lesions. Accordingly, milking machine control and milking technique evaluation might help in decreasing the incidence of teat lesions, together with correct constructed stalls and good hoof care. These factors should receive attention in dairy herd health programmes.

Desipramine in small doses induces antinociception in the increasing temperature hot-plate test, but not in the tail-flick test

The data reported for the antinociceptive effect of tricyclic antidepressants are conflicting. In this investigation, the effect of acute intraperitoneal (i.p.) administration of desipramine (2 and 5 mg/kg) was studied in rats, using the tail-flick test with simultaneous measurement of tail-skin temperature, and the increasing temperature hot-plate test. A constant negative correlation between tail-flick latency and tail-skin temperature, as described earlier, was also found in this study. Different ambient temperatures influenced the results of the tail-flick test. At an ambient temperature of 24-25 degrees C, desipramine gave rise to an apparent antinociception in the tail-flick test, which was found to be caused by a relative fall in tail-skin temperature. At 21-22 degrees C, no change in tail-flick latency was found after the administration of desipramine. In the increasing temperature hot-plate test, however, a dose-dependent antinociceptive effect of desipramine was observed at both ambient temperatures. The strong influence of moderate differences in ambient temperature on the results of the tail-flick test may explain some of the conflicting results reported in the literature. Whenever this test is used, the temperature of the tail should be recorded and taken into account in the evaluation of the data.

The apparent hyperalgesic effect of a serotonin antagonist in the tail flick test is mainly due to increased tail skin temperature

It has been suggested that reduced activity in raphe-spinal serotonergic systems induces hyperalgesia. In rats, the serotonin antagonist metergoline (0.5 mg/kg intraperitoneally) reduced tail flick latency by 0.92 sec (p less than 0.001) and increased tail skin temperature by 2.4 degrees C (p less than 0.001) when measured 50 min after injection. Multiple regression analysis with tail flick latency as dependent variable and tail skin temperature and metergoline/vehicle as independent variables revealed a highly significant effect of tail temperature on tail flick latency. The increase of tail skin temperature explained a reduction of tail flick latency of 0.64 of the 0.92 sec observed [B = -0.267 +/- 0.034, t(37)= -7.75, p less than 0.0001]. When the effect on tail skin temperature was taken into account, metergoline reduced tail flick latency by 0.28 sec [B = -0.284 +/- 0.114, t(37) = -2.50, p less than 0.05]. Metergoline (0.5 and 2.0 mg/kg) did not significantly alter plantar paw skin temperature or the response temperature in the increasing temperature hot plate test. Thus, the observed effect of metergoline on tail flick latency is primarily due to an effect on tail skin temperature. The possibility exists that the remaining effect of metergoline may be due to inadequate correction for the skin temperature change, and it is concluded that the study provide no clear evidence for a tonic inhibition of nociception by serotonergic systems.

Effect of a shielded liner on new mastitis infection

Results from a field trial involving 23 Norwegian dairy herds support the theory that deflector shields inserted into the teatcup liner can reduce the risk of intramammary infection. However, the effectiveness of this measure is questionable in cows already infected and in problem herds.