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.

An improved method for tail-flick testing with adjustment for tail-skin temperature

The tail-skin temperature is an important factor in determining tail-flick latency to noxious radiant heat in rats and mice. A simple, non-invasive method for recording the tail-skin temperature during conventional tail-flick testing is described. The method is conveniently performed during conventional tail-flick testing. It does not require additional handling of the animals, and it is not stressful. The method utilizes a small-sized thermocouple which is brought in contact with the dorsal surface of the tail close to the area exposed to the radiant heat stimulus. A computer based system is used to record the temperature and control the tail-flick apparatus. Continuous monitoring of skin temperature showed that the temperature as measured 23 mm from the tip of the tail agreed well with skin temperature in the position where the beam was focused during tail-flick testing (13 mm from the tip). The skin temperature closer to the base of the tail (100 mm from the tip) showed considerably more deviation from the temperature 13 mm from the tip. Temperature measurements close to the heated area gave a higher degree of correlation between recorded temperature and tail-flick latencies than did temperature measurements closer to the base of the tail. These results provide further support for the contention that tail-skin temperature is an important factor when assessing nociception by means of the tail-flick test, and demonstrate that the temperature should be measured as close to the heated area as possible.

Rapid isolation of K88+ Escherichia coli by using immunomagnetic particles

Superparamagnetic polymer particles precoated with sheep anti-mouse immunoglobulin G were coated with immunoglobulin G2 monoclonal antibodies to the K88 antigen of Escherichia coli (MAb-K88). These immunomagnetic particles (IMP) were used for isolation and identification of K88 antigen-positive (K88+) E. coli. The bacteria presenting the K88 antigen were easily isolated in almost pure culture from a mixed culture of five different O serogroups of E. coli. Nonspecific binding of K88 antigen-negative (K88-) E. coli to the IMP was not observed. The sensitivity of the test to detect K88+ E. coli was found to be 4,000 CFU/ml with fluorescence microscopy. When bacteria attached to the MAb-K88 IMP were grown on blood agar, about 20% of the initial number of CFU was recovered. The test is promising as a rapid method for isolation and identification of K88+ E. coli from a mixed culture.

The role of antiepileptics in sudden death in epilepsy

In a material of sudden, unexpected death of epileptic patients treated with one or more of the anticonvulsants phenobarbitone, phenytoin and carbamazepine we found subtherapeutic drug levels in half of the cases and lethal concentrations, mainly of phenobarbitone, in one third of the cases. The results illustrate the severe consequences of noncompliance in epilepsy, and stress the value of blood drug level control.

The diagnostic value of postmortem blood glucose determinations in cases of diabetes mellitus

In 24 cases of death in diabetic coma the peripheral venous blood showed glucose levels exceeding 3.5 mg/ml (mean value 7.76 mg/ml). In a control material of deaths of other causes the blood glucose was usually low and often zero, and all values were well below the lower limit of the diabetic concentrations. The acetone contents of the diabetic blood varied widely and were of limited diagnostic value. We conclude that glucose concentrations above 3.5 mg/ml in the peripheral blood indicate that death occurred in diabetic coma.

The causes of death in fire victims

In 169 consecutive cases of autopsied fire victims about 50% had lethal levels of carboxyhemoglobin. Soot in the respiratory tract was found in about 90% of the cases. The age distribution of the fire victims showed significantly less persons in the 15-35-year group than should be expected according to the age distribution of the population, presumably due to greater agility of younger people. More than half of the fire victims had alcohol in the blood exceeding 0.05%, and alcohol intoxication should be considered accessary to many deaths in fire. The characteristic biphasic distribution of carboxyhemoglobin in fire victims together with other observations suggest that the principal causes of death are carbon monoxide followed by carbon dioxide poisoning and/or oxygen deficiency, while the influence of heat is considered to be of minor importance.

Differences in bindings to the GM1 receptor by heat-labile enterotoxin of human and porcine Escherichia coli strains

Heat-labile enterotoxin producing strains of Escherichia coli were isolated from diarrheal faeces of humans and from the jejunum of pigs which had died of diarrhea. The heat-labile enterotoxin was assayed by three different enzyme-linked immunosorbent assays (ELISA). The first assay was based upon immunological cross-reactions between the heat-labile enterotoxins of E coli and Vibrio cholerae, the second on specific E coli heat-labile enterotoxin antibodies and the third on affinity of the toxin to the presumed cell membrane receptor, the ganglioside GM1. The heat-labile enterotoxins of human and porcine origin bound equally well to the same extent in the ELISA procedure, which utilized immunological cross-reactivity between the heat-labile enterotoxins of E coli and V cholerae. The reactivity, however, was quite different in the GM1-ELISA. The binding affinity was high between GM1 and enterotoxin produced by E coli strains of human origin, whereas the binding affinity was low for enterotoxin from porcine strains.