The signal recognition particle database (SRPDB).

The SRPDB (signal recognition particle database) provides annotated SRP RNA sequences from Eucaryotes and Archaea, phylogenetically ordered and aligned with their bacterial equivalents. We also make available representative RNA secondary structure diagrams, where each base pair is proven by comparative sequence analysis. New to this release are 17 SRP RNA sequences (a total of 64 sequences) and alignments of proteins SRP19 and SRP54 with their RNA binding sites.     

Visual performance of the toad (Bufo bufo) at low light levels: retinal ganglion cell responses and prey-catching accuracy

The accuracy of toad snapping towards moving worm dummies under various levels of dim illumination (from absolute threshold to moonlight) was videorecorded and related to spike responses of retinal ganglion cells exposed to equivalent stimuli. Some toads (at ca. 16 °C) successfully snapped at dummies that produced only one photoisomerization per 50 rods per second in the retina, in good agreement with thresholds of sensitive retinal ganglion cells. One factor underlying such high sensitivity is extensive temporal summation by the ganglion cells. This, however, is inevitably accompanied by very long response latencies (around 3 s near threshold), whereby the information reaching the brain shows the dummy in a position where it was several seconds earlier. Indeed, as the light was dimmed, snaps were displaced successively further to the rear of the dummy, finally missing it. The results in weak but clearly supra-threshold illumination indicate that snaps were aimed at the advancing head as seen by the brain, but landed further backwards in proportion to the retinal latency. Near absolute threshold, however, accuracy was too good, suggesting that the animal had recourse to a neural representation of the regularly moving dummies to correct for the slowness of vision.     

Egg attendance and brooding by males of the giant water bugLethocerus medius (Guerin) in the field (Heteroptera: Belostomatidae)

Males of the giant water bug Lethocerus medius(Guerin) typify their monobasic subfamily, the Lethocerinae, in that they do not brood eggs attached to their backs as do males of all members of the subfamily Belostomatinae. Exclusive male parental investment as expressed in the Belostomatinae is extremely rare behavior among animals, and evolution of the trait is obscure. Lethocerus mediusmales apparently remain with their mates through oviposition and are consistently found in attendance of eggs after the female has departed. This behavior may enhance paternity assurance at no cost in opportunity for polygyny. Two double clutches of eggs were found, from which we infer the potential for polygynous matings and shared parental investment. Male L. mediusbrood attended egg clutches above the surface of the water, where they may moisten them, shade them, and defend them against predation. Egg attendance/brooding by L. mediusand other Lethocerusspecies may represent a plesiomorphic state from which paternal back- brooding evolved in the Belostomatinae.     

Substance P in the suprachiasmatic nucleus of the rat: an immunohistochemical and in situ hybridization study

Using a biotin-streptavidin-horseradish peroxidase (HRP) immunohistochemical technique the distribution of substance P-immunoreactive neuronal elements was investigated in the rat suprachiasmatic nucleus (SCN). Substance P-immunoreactive nerve fibres and varicosities were distributed throughout the suprachiasmatic nucleus, with the largest accumulation in its ventral part. Because this location overlaps with the innervation of retinal afferents, the distribution and density of substance P-immunoreactive fibres in bilaterally enucleated rats were compared to normal rats. The density of substance P-immunoreactive fibres and nerve terminals in the ventral part of the suprachiasmatic nuclei was reduced in the rats with bilateral destruction of the optic nerves, whereas the density of fibres and nerve terminals in the dorsal part as well as other retinal target areas in the thalamus and mesencephalon was unaffected. In rats pretreated with an intraventricular injection of colchicine several substance P-immunoreactive perikarya were identified in the suprachiasmatic nucleus. The immunoreactive neurons, measuring 9.7 m±1.1 m in diameter, were frequently observed in the central core of the nucleus and to a lesser extent in the dorsomedial and ventrolateral subparts. Using in situ hybridization histochemistry pre-protachykinin-A mRNA was found in the same part of the SCN indicating that synthesis of substance P takes place in SCN neurons. Using a double immunohistochemical approach applying diaminobenzidine and benzidinedihydrochloride as chromagens substance P-, vasoactive intestinal peptide (VIP)-, and vasopressin/neurophysin-immunoreactivities were identified in the same brain section. The substance P-immunoreactive perikarya constituted a separate population of SCN neurons, which were not vasopressin-, neurophysin- or VIP-immunoreactive. Taken together, these observations show that substance P is contained in the retinohypothalamic pathway and within a group of SCN cell bodies, indiating that substance P may play a role in the generation and entrainment of circadian rhythmicity.     

Effect of Dietary Magnesium on Post Mortem Phosphocreatine Utilization in Skeletal Muscle of Swine: A Non-Invasive Study Using 31P-NMR Spectroscopy

The effect of dietary magnesium on the post mortem PCr (phosphocreatine) decay in muscle of heterozygote malignant hyperthermia pigs was studied after in vivo exposure to a combination of halothane and succinylcholine. The pigs were anaesthetized with halothane and succinylcholine was injected in the ear vein. Immediately after initiation of the depolarizing neuromuscular blocking effect of succinylcholine the animals were captive-bolt stunned. The PCr decay, reflecting ATP turnover, was followed in situ by 31P-NMR spectroscopy in the biceps femoris muscle for the subsequent 40-70 min post mortem. In 3 of the 4 experiments, the Mg-fed pig had a significantly reduced rate of PCr hydrolysis compared to the control animal. The mechanism of this magnesium effect is unknown.     

Atypical Aeromonas salmonicida Isolated from Diseased Turbot (Scophtalmus maximus L.)

Atypical Aeromonas salmonicida were isolated from 3 outbreaks of disease among farmed turbot (Scophthalmus maximus L.) in 3 different farms, 1 from Norway (Nl) and 2 from Denmark (DK1 and DK2). In all 3 cases, the incidence of disease and mortality was high and the main characteristic pathological finding was skin ulcers and septicaemia. The isolated bacteria were subjected to a thorough phenotypic and genotypic examination and comparison in the laboratory. All 3 isolates belonged to A. salmonicida but dis-played some very different biochemical properties. However, the 2 Danish strains, DK1 and DK2 had identical ribotypes but different from that of Nl, whereas the plasmid pro-files of DK1 and Nl were identical but different from that of DK2. These observations emphasize the need for an improvement of our understanding of the taxonomy and epi-demiology of atypical A. salmonicida.     

Acute Post-Treatment Enterocolitis in 13 Horses Treated in a Norwegian Surgical Ward

Case histories, results of laboratory analyses, treatment regimens and outcome are de-scribed for 13 horses that developed acute enterocolitis after various surgical treatments. Twelve of the 13 horses had been cast in lateral recumbency, and 10 of those 12 had re-ceived general anesthesia. Eleven horses had been treated with antimicrobial drugs. Most horses (11) developed diarrhea 2 days after initiation of treatment, with a variation from 1 to 5 days. The most apparent symptoms were fever, up to 40.5°C, elevated heart rate, discoloration of mucous membranes, and diarrhea. Dehydration, acidosis and leu-kopenia were marked at the time clinical signs occurred. Packed cell volume and total serum protein values were elevated. Therapy was directed toward replacement of fluid losses, restoration of acid-base balance, and counteraction of inflammation. Seven horses (54%) died or were euthanized. At necropsy, pathological changes showed large variations between individuals. Salmonella spp. were not isolated from any of the horses, and no common causative agent was identified. Preventive efforts to avoid post-treatment enterocolitis have been taken with regard to preoperative routines, premedic-ation and anesthesia, with apparent success.     

Purification and characterization of dihydroorotate dehydrogenase A from Lactococcus lactis, crystallization and preliminary X-ray diffraction studies of the enzyme.

Lactococcus lactis is the only organism known to contain two dihydroorotate dehydrogenases, i.e., the A- and B-forms. In this paper, we report the overproduction, purification, and crystallization of dihydroorotate dehydrogenase A. In solution, the enzyme is bright yellow. It is a dimer of subunits (34 kDa) that contain one molecule of flavin mononucleotide each. The enzyme shows optimal function in the pH range 7.5-9.0. It is specific for L-dihydroorotate as substrate and can use dichlorophenolindophenol, potassium hexacyanoferrate (III), and, to a lower extent, also molecular oxygen as acceptors of the reducing equivalents, whereas the pyridine nucleotide coenzymes (NAD+, NADP+) and the respiratory quinones (i.e., vitamins Q6, Q10 and K2) were inactive. The enzyme has been crystallized from solutions of 30% polyethylene glycol, 0.2 M sodium acetate, and 0.1 M Tris-HCl, pH 8.5. The resulting yellow crystals diffracted well and showed little sign of radiation damage during diffraction experiments. The crystals are monoclinic, space group P21 with unit cell dimensions a = 54.19 A, b = 109.23 A, c = 67.17 A, and beta = 104.5 degrees. A native data set has been collected with a completeness of 99.3% to 2.0 A and an Rsym value of 5.2%. Analysis of the solvent content and the self-rotation function indicates that the two subunits in the asymmetric unit are related by a noncrystallographic twofold axis perpendicular to the crystallographic b and c axes.     

Backbone Cyclization of the C-terminal Part of Substance P. Part 1: The Important Role of the Sulphur in Position 11

Novel backbone-to-side chain and backbone-to-backbone cyclic analogues of substance P (SP) were prepared by solid-phase synthesis and screened for biological activity. An analogue containing a thioether- lactam ring between positions 9 and 11 showed an EC₅₀ value of 20nM toward the neurokinin 1 (NK-1) and was inactive toward the NK-2 and NK-3 receptors. On the other hand, in a multiple backbone cyclic peptide library of similar analogues, in which the sulphur was excluded from the ring, very low activity was detected. The activity was re-evaluated and was found to be even lower (EC₅₀=0.11 mM ) than the previously published data. These results indicate that the thioether moiety has a crucial role in receptor activation. The results also show tolerance of the NK-1 receptor, but not NK-2 or NK-3, to cyclization of the C-terminal portion of the SP_6–11 hexapeptide.