Interdigestive myoelectric activity in rat intestine has been recorded and characterized. The interdigestive pattern of activity can be disrupted by oral glucose and high doses of the duodenal ulcerogen cysteamine. Intravenous glucose had no effect on the interdigestive myoelectric pattern, nor did high doses of porcine motilin. Attempts were made to develop a hybridoma cell line secreting antibodies that would recognize rat Intestinal immunoreactive motilin (IR-M). The murine myeloma cell line NS1 was fused with murine B-cells primed against porcine motilin. One hundred of the monoclonal cell lines produced secreted monoclonal antibodies that recognized porcine motilin. Attempts to identify a cell line secreting antibodies with the ability to stain rat intestinal tissue, however, produced only negative results. Rat intestinal IR-M has been characterized with respect to immunocytochemistry (ICC), radioimmunoassay (RIA), and chromatographic properties. The biological activity of partially purified rat intestinal IR-M has also been evaluated utilizing a rabbit isolated duodenal muscle strip preparation. Five different antisera and one monoclonal antibody directed against natural porcine motilin were utilized in an effort to detect IR-M containing cells in rat intestinal tissues. A variety of techniques were employed including tissue fixation with either Bouins, paraformaldehyde, or benzoquinone. In addition a variety of staining methods including, fluorescein conjugated second antibody, peroxidase-antiperoxidase or peroxidase conjugated second antibody techniques were used. All methods using these antibodies failed to detect IR-H in the rat small intestine. Porcine motilin was able to displace ¹²⁵I-motilin from antisera 13-3, 72X and M03. These antisera were utilized in a motilin RIA to evaluate acid extracts of rat intestinal tissue for IR-M. Only antisera 13-3 and 72X were capable of detecting IR-M in gut extracts, and these antisera gave different distributions of IR-M In the proximal small bowel. Rat intestinal tissue was extracted into 2% trifluoroacetic acid and the soluble fraction clarified by centrifugation. This acid extracted material was precipitated with sodium chloride then dissolved in methanol at pH 6.0. Methanol soluble material was precipitated with ether and the ether precipitate then dissolved in water and chromatographed on Sep-Pak C₁₈ cartridges (Waters). Sep-Pak cartridges were eluted with 50% acetonitrile: 0.1% TFA. The 50% eluate was then fractionated further using cation exchange, gel filtration and reverse phase high pressure liquid chromatography (HPLC). Rat intestinal IR-M peaks from cation exchange chromatography on SP-Sephadex-C25 (Pharmacia) were concentrated and examined for contractility in a rabbit duodenal muscle strip preparation. Purification after SP-Sephadex-C25 was approximately 20 fold. Desensitization of rabbit duodenum to porcine motilin could be demonstrated by pre-treatment with motilin. Contractile activity of partially purified rat intestinal IR-M was not inhibited by pretreatment with motilin. Chromatography on Bio-Gel P-10 (Biorad) eluted with 0.2M acetic HPLC, using a linear gradient of water/acetonitrile (10-45% acetonitrile in 30 min), rat intestinal IR-M did not co-elute with natural porcine motilin. In conclusion, the molecular weight of rat intestinal IR-M appeared to be similar to porci ne motilin as these two substances demonstrated co-elution on gel permeation chromatography. The lack of co-elution with porcine motilin on HPLC indicates that other molecular characteristics of rat intestinal IR-M, such as hydrophobicity, are not similar to porcine motilin. Furthermore, partially purified rat intestinal IR-M did induce a contractile response in rabbit duodenal muscle strips but porcine motilin did not desensitize this preparation to the contractile activity of rat intestinal extracts. This suggests that the contractile activity of these two compounds is induced via different receptor mechanisms. It is concluded that the immunoreactive motilin found in rat intestinal extracts does not resemble natural porcine motilin in structure or biological activity. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

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No description available.

Dissertation (MSc)--University of Pretoria, 2007. / Zoology and Entomology / Unrestricted

Tissue thiamin diphosphate was assayed enzymatically utilizing purified brewer's yeast apotransketolase. With this assay ten uumoles of thiamin diphosphate could be detected. Total thiamin was fluorometrically measured. For one to three days rats were placed under conditions of stress, consisting of loud noise treatment, emotional stress, deprivation of paradoxical sleep, and swimming to exhaustion, respectively. The body weight was markedly decreased at the end of the respective experimental periods except with the loud noise treated group, compared with the corresponding controls. Following two to three such consecutive treatments, the adrenal weight also showed a significant increase. Thiamin diphosphate and total thiamin in liver was significantly decreased after one day's exposure to loud noise. On the other hand, thiamin diphosphate and total thiamin in brain and liver were not significantly affected by the other treatments tried in this study .

Since the isolation of triiodothyronine (T3) by Pitt-Rivers and Gross (1953) several questions as to its role as a thyroid hormone arose. Does T3 have the same or different actions than that of thyroxine (T4 )? Is T3 an emergency hormone, since its synthesis relative to T4 is greatly increased during periods of low iodine intake and its response time is I/5th that of T4 (Ackerman and Arons, 1958)? Are there any interactions modifying their respective actions?

The determination of total thiamin, free thiamin, thiamin di phosphate (TDP) plus thiamin triphosphate (TTP), and total α- hydroxyethylthiamin (HET) levels in rat brain in control, deficient, oxythiamin- (OTH) and pyrithiamin- (PTH) treated rats was accomplished. It was found that the TDP + TTP/thiamin ratio observed in the thiamin-deficient, OTH- and PTH-treated rats was constant and did not differ from the ratio observed in the control rat brains. The brain levels of TDP + TTP decreased to 39% and 12% of the control thiamin levels in deficient and PTH-treated rats respectively. The brain HET and TDP + TTP levels of the OTH-treated rats were not significantly different from the controls. The HET levels in the PTH rats decreased significantly ( α = 0.005) by treatment day 4 and decreased to one-seventh of the control values in the terminal stages. A significant drop in the HET levels from the control levels was interpreted to mean that the pyruvate utilization was significantly impaired in the brain.

To examine the effect of a central noradrenergic lesion on the reactivity of the 5-HT1B receptor we compared intact male rats with rats in which noradrenergic nerve terminals were largely destroyed with the neurotoxin DSP-4 (50 mg/kg × 2, on the 1st and 3rd days of postnatal life). When rats attained 10 weeks of age, control and DSP-4 rats were divided into two subgroups receiving either saline or the serotonin (5-HT) synthesis inhibitor (p-chlorophenylalanine; p-CPA; 100 mg/kg). Employing an elevated plus maze test, we demonstrated that CP 94,253 (5-propoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-pyrrolo[3,2-b]pyridine hydrochloride)(4.0 mg/kg; 5-HT1B agonist) induced an anxiogenic-like action in control rats; however, it failed to elicit this effect in the DSP-4 group. Surprisingly, in p-CPApretreated rats anxiogenic-like activity was observed both in control and DSP-4 treated rats. CP 94,253 significantly attenuated 5-HT synthesis in the medial prefrontal cortex (mPFC) of control rats, and SB 216641 (N-{3-[3-(dimethylamino) ethoxy]-4-methoxyphenyl}-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-[1,1'-biphenyl]-4-carboxamide hydrochloride) (4.0 mg/kg; 5-HT1B antagonist) was able to antagonize this effect. Conversely, CP 94,253 failed to significantly inhibit the 5-HT synthesis rate in DSP-4-treated rats. In the microdialysis study CP 94,253 induced long-lasting attenuation of 5-HT release in the mPFC of control rats but had no effect in DSP-4 rats. These data lead to the proposal that presynaptic 5-HT1B autoreceptors underwent desensitization in DSP-4 treated rats.

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015 / The free radical theory of aging postulates that accumulation of oxidative damage in major cellular components is the predominant underlying cause of the aging phenotype. This damage is caused most commonly by reactive oxygen species (ROS) and antioxidant enzymes such as the superoxide dismutases (SOD) that neutralize ROS, are therefore vital. Manganese superoxide dismutase (MnSOD) is particularly critical as it is functional in the mitochondria, a major site for ROS generation. Numerous studies have demonstrated a tissue-specific decrease in the activity and mRNA levels of major antioxidants, including MnSOD, with aging, however the exact mechanism of this regulation is unclear. It was hypothesized that a general down-regulation of various antioxidant enzymes such as this may occur at the transcriptional level. In order to investigate SOD2 regulation, a comprehensively annotated rat SOD2 promoter region was established using the appropriate bioinformatics tools. Following this, SOD2 mRNA levels in tissues from young and old rat tissue were compared using quantitative PCR. The results showed increased and decreased SOD2 mRNA levels in old compared to young liver tissue and brain tissue, respectively, however these trends were not statistically significant. As MnSOD has been shown to be epigenetically downregulated in various age-related diseases it was hypothesized that the decrease in MnSOD mRNA levels seen in aging brain tissue may be a result of epigenetic regulation at the SOD2 (MnSOD gene) promoter, specifically, through DNA methylation. A methylation assay assessing the SOD2 gene promoter revealed no significant evidence of hypermethylation. Although this suggests that promoter methylation is an unlikely mechanism of SOD2 regulation in aging, further work would need to be implemented in order to prove this conclusively.

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