The N-acetylation of arsanilic acid In vitro by mammalian enzymes.
The N-acetylation of arsanilic acid was assayed in vitro by modifying a literature method for acetylation of p-aminobenzoic acid. Conditions included final concentrations of 1.0 mM dithiothreitol, 1.0 mM EDTA, 0.45 mM acetyl coenzyme A, an acetyl coenzyme A regenerating system using bacterial phosphotransacetylase and acetyl phosphate, 5.0 mM arsanilate substrate, and 25 mM sodium/potassium phosphate buffer, pH 7.4, in a total volume of 0.5 ml. Incubation was at 37 degrees C, with 0.5- to 2-mg N-acetyltransferase enzyme protein from a preparation of guinea pig liver. The reaction was terminated by heat precipitation. The resulting supernatant was put through a 4 mm 0.45 microm polysulfone membrane syringe filter. The filtrate could then be injected directly onto the HPLC. With arsanilic acid as substrate, the product N-acetylarsanilic acid (NAA) was identified by its retention time (33 min) in the HPLC system of the laboratory. The 33-min fraction collected from the HPLC was scanned and gave the characteristic UV spectrum of NAA, with peaks at 203 and 256 nm. In addition, the product comigrated in the HPLC system with standard NAA. Under comparable assay conditions, the N-acetylation of arsanilate by the guinea pig enzyme preparation is about 24% the rate of that of the model substrate p-aminobenzoic acid. Typical activity for arsanilate acetylation was 0.5 nmol/min/mg enzyme protein. Using the same assay system and HPLC detection method, the supernatant from bacterial lysates containing recombinant human N-acetyltransferase 1 exhibited acetylation activity toward arsanilate of 720 nmol/min/mg enzyme protein. (+info)
Vestibular information is required for dead reckoning in the rat.
Dead reckoning is an on-line form of spatial navigation used by an animal to identify its present location and return directly to a starting location, even after circuitous outward trips. At present, it is not known which of several self-movement cues (efferent copy from movement commands, proprioceptive information, sensory flow, or vestibular information) are used to compute homeward trajectories. To determine whether vestibular information is important for dead reckoning, the impact of chemical labyrinthectomy was evaluated in a test that demanded on-line computation of a homeward trajectory. Rats were habituated to leave a refuge that was visible from all locations on a circular table to forage for large food pellets, which they carried back to the refuge to eat. Two different probe trials were given: (1) the rats foraged from the same spatial location from a hidden refuge in the light and so were able to use visual cues to navigate; (2) the same procedure took place in the dark, constraining the animals to dead reckon. Although control rats carried food directly and rapidly back to the refuge on both probes, the rats with vestibular lesions were able to do so on the hidden refuge but not on the dark probe. The scores of vestibular reflex tests predicted the dead reckoning deficit. The vestibular animals were also impaired in learning a new piloting task. This is the first unambiguous demonstration that vestibular information is used in dead reckoning and also contributes to piloting. (+info)
Strong galvanic vestibular stimulation obscures arterial pressure response to gravitational change in conscious rats.
Galvanic vestibular stimulation (GVS) is known to create an imbalance in the vestibular inputs; thus it is possible that the simultaneously applied GVS obscures adequate gravity-based inputs to the vestibular organs or modifies an input-output relationship of the vestibular system and then impairs the vestibular-mediated response. To examine this, arterial pressure (AP) response to gravitational change was examined in conscious rats with and without GVS. Free drop-induced microgravity and centrifugation-induced hypergravity were employed to elicit vestibular-mediated AP response. GVS itself induced pressor response in an intensity-dependent manner. This pressor response was completely abolished by vestibular lesion, suggesting that the GVS-induced response was mediated by the vestibular system. The pressor response to microgravity (35 +/- 3 mmHg) was significantly reduced by simultaneously applied GVS (19 +/- 1 mmHg), and pressor response to 3-G load was also significantly reduced by GVS. However, GVS had no effect on air jet-induced pressor response. The effects of GVS on pressor response to gravitational change were qualitatively and quantitatively similar to that caused by the vestibular lesion, effects of which were demonstrated in our previous studies (Gotoh TM, Fujiki N, Matsuda T, Gao S, Morita H. Am J Physiol Regul Integr Comp Physiol 286: R25-R30, 2004; Matsuda T, Gotoh TM, Tanaka K, Gao S, Morita H. Brain Res 1028: 140-147, 2004; Tanaka K, Gotoh TM, Awazu C, Morita H. Neurosci Lett 397: 40-43, 2006). These results indicate that GVS reduced the vestibular-mediated pressor response to gravitational change but has no effect on the non-vestibular-mediated pressor response. Thus GVS might be employed for the acute interruption of the AP response to gravitational change. (+info)
Vestibular-mediated increase in central serotonin plays an important role in hypergravity-induced hypophagia in rats.
DNA damage and decrease of cellular oxidase activity in piglet Sertoli cells exposed to arsanilic acid.
The study was designed to explore the toxic effects of arsanilic acid on piglet Sertoli cells. Sertoli cells were isolated from piglet testes using a two-step enzyme digestion followed by differential plating. Piglet Sertoli cells were cultured and classified into the following five groups: group A, the control without arsanilic acid treatment; group B, cultured with 5 microM arsanilic acid; group C, cultured with 50 microM arsanilic acid; group D, cultured with 0.5 mM arsanilic acid; and group E, cultured with 5 mM arsanilic acid. We found that Sertoli cell growth was inhibited by arsanilic acid at 0.5 mM compared with the control, group A. The oxidase activity of Sertoli cells was decreased by arsanilic acid at 0.5 mM as evidenced by the observations that arsanilic acid increased MDA content but decreased the SOD and GSH-Px activities of Sertoli cells. Moreover, 50 microM of arsanilic acid was observed to cause DNA damage in Sertoli cells. The results of our study suggest that exposure of Sertoli cells to arsanilic acid leads to induction of oxidative stress and inhibition of cell growth at a high concentration, while arsanilic acid causes DNA damage in Sertoli cells at a low concentration. (+info)
Affinity maturation in the arsonate system: lack of dominance of high-affinity antibody subpopulations.
Affinity maturation was studied by the analysis of the kinetics of the appearance of antibody subpopulations with different affinities during the immune response, using an hapten-inhibition ELISA. The immune response in KLH-Ar-immunized A/J mice was used as a model system. Five antibody subpopulations of different affinity (10(3)-10(7) M-1) could be detected, the relative concentrations of which changed during affinity maturation. The high-affinity antibody subpopulations did not represent the major fraction at any stage during affinity maturation. The appearance of the highest affinity subpopulation (10(7) M-1), despite exhibiting relative concentrations no higher than 12%, produced an important increase in average affinity. On the other hand, its disappearance at the end of the maturation process could explain the average affinity decrease observed at this stage. Our results indicate that affinity maturation cannot be explained by the dominance of high-affinity clones, as proposed by Siskind & Benacerraf (1969). The increase in affinity could rather be due to the progressive appearance of low percentages of high-affinity clones, which are not present in the primary response and never become dominant. (+info)
Feeding sodium arsanilate for exciting diarrhea and identifying carriers of swine dysentery.
Sodium arsanilate was fed to nondiarrhetic swine, previously exposed to and treated for swine dysentery, for the purpose of inducing them into developing a swine dysentery diarrhea. From 40 to 100% of these swine in each pen had previously had a swine dysentery diarrhea. The isolate of Treponema hyodysenteriae in the diced colon which was used to expose the swine was resistant to sodium arsanilate. After an interim of no treatment for swine dysentery, sodium arsanilate was fed at a level of 220 parts per million for 21 days. Of the 14 pens containing swine fed sodium arsanilate, ten pens had one or more swine that developed a swine dysentery diarrhea while being fed sodium arsanilate. This was significantly (P less than 0.05) greater than the three pens that each had one pig that developed a swine dysentery diarrhea of 13 pens containing similar swine not fed sodium arsanilate during a comparable period. In the 14 pens containing swine fed sodium arsanilate, 14 swine were the first to develop a swine dysentery diarrhea since in four pens, two swine in each pen developed diarrhea within 24 hours of each other. This also was significantly (P less than 0.01) greater than the three swine in the ten pens not fed sodium arsanilate. From these results, it was theorized that sodium arsanilate excited the nondiarrhetic carrier into developing a swine dysentery diarrhea and that this phenomenon may have potential in identifying the carrier state. (+info)
Probable elimination of swine dysentery after feeding ronidazole, carbadox or lincomycin and verification by feeding sodium arsanilate.
Swine dysentery did not recur during a nine week period after withdrawal of medication in swine fed ronidazole at a level of 60 parts per million of feed for ten weeks or fed either carbadox at 55 ppm or lincomycin at 110 ppm of feed for six weeks. During this period swine dysentery was neither transmitted to accompanying sentinels after the withdrawal of the above medication or was Treponema hyodysenteriae isolated and cultured or observed in stained smears from rectal swabs and feces or from colonic scrapings at necropsy. Beginning three weeks after the withdrawal of medication, all swine were fed sodium arsanilate at a concentration of 220 ppm of feed for three weeks in an attempt to excite the carrier of swine dysentery into developing a swine dysentery diarrhea. A swine dysentery diarrhea did recur during the feeding of sodium arsanilate in swine previously fed ronidazole at a level of 60 ppm of feed for only six weeks. It was concluded: that swine dysentery was probably eliminated with the feeding of ronidazole for the longer duration and with the feeding of carbadox and lincomycin and that sodium arsanilate was of value in identifying the carrier state. (+info)