The defecation reflex in rats: fundamental properties and the reflex center

While pharmacological and physiological studies in rats are now increasing, physiological properties of their defecation have been scarcely investigated. This study was performed to define the properties of defecation in decerebrate rats, with special reference to the pontine defecation reflex center, which has been postulated in dogs. Intraluminal pressure was recorded from the colon and rectum with balloon-pressure transducer method using balloons of 15-20 mm in length and 0.1-0.3 ml in volume. Distention of a balloon in the descending colon and rectum with an additional injection of 0.03-0.1 ml air induced propulsive contractions on the descending colon and rectum. The mean of threshold pressures to induce propulsive contraction was 17.0 +/- 5.8 mm Hg (mean+/-S.E.) in the proximal part and 18.3 +/- 3.3 mm Hg in the distal part of the descending colon, and 11.8 +/- 1.3 mm Hg in the rectum. The maximum amplitude of propulsive contractions was 55 mm Hg in the rectum, 47 mm Hg in the distal part of the descending colon and 38 mm Hg in the proximal part. Similar colorectal propulsive contractions were produced by gastric distention (5-10 ml, 20-30 mm Hg) and electrical stimulation of the anal canal. Contrarily, spontaneous contractions of the proximal colon were suppressed by rectal distention and anal-canal stimulation. These results suggest that the descending colon and rectum, but not the proximal colon, were innervated by the pelvic afferent and efferent fibers mediating the defecation reflex. Pontine transection at the cerebellar peduncle level abolished colorectal propulsive contractions induced by distention of the stomach, descending colon and rectum, and stimulation of the anal canal, although much smaller contractions were still induced after the pontine transection. These results suggest that the pontine defecation reflex center exists and works in rats, as in dogs.     

Effects of melanocyte-stimulating hormone (MSH) and melatonin on passive avoidance and on an emotional response

The present experiment investigated the opposite effects of synthetic α-MSH and Melatonin on acquisition and extinction of a passive avoidance response (PAR) and on emotionality, as indexed by defecation, in the PA box. It was found that intraperitoneal (IP) administration of α-MSH delayed extinction and increased defecation responses whereas IP administration of Melatonin facilitated extinction of the PAR and decreased defecation. The present experiment confirmed MSH-Melatonin opposition on memory and on the defecation response.     

Stress, behavioral arousal, and open field activity—A reexamination of emotionality in the rat

The effects of stress upon emotionality, and of emotionality upon the open field activity of rats have now been studied for over four decades. Controversy remains however regarding the degree to which stress alters behavior, and the direction of that change. One reason for this is the absence of an adequate behavioral definition of stress. The present series of experiments demonstrates a standard relatively nontraumatic stress induction procedure which may be used in conjunction with open field testing. Pre-exposure to moderately intense light and white noise facilitated open field activity as measured by initial activity, lowered defecation scores, and supplementary measures (rearing, grooming, center field penetration). Further parametric, psychoendocrine, and pharmacological studies characterized the nature of the facilitation, its time course, and its modification by other manipulations. Our results suggest the initial behavioral response to stress in an open field is activation. Previous studies may have differed in their results relating stress and behavior because of subtle procedural distinctions, some of which may be identified using the present technique.     

Biological cycle and preliminary data on vectorial competence of Triatoma boliviana in laboratory conditions

With more than 140 potential vectors of Chagas disease, it is important to better know the biology and especially the vectorial capacity of the triatomine species which live in the surroundings of human dwellings. In Bolivia where 17 triatomine species are reported, the principal vector is Triatoma infestans. In some valleys of the department of La Paz where T. infestans is not present, a new species (Triatoma boliviana) was described in 2007. This species lives in a sylvatic environment not far away from the dwellings, and occasionally some individuals are found inside the houses. This study was carried out to describe the biological cycle of T. boliviana and to determine its vectorial competence. The development of a cohort of 95 nymphs of first instar (N1) was followed through nymphal instars and adult stage until death in laboratory (22 °C). They were fed twice a week on an immobilized mouse. The median egg-to-adult development time was 8.4 months. The mortality by nymphal instar was lower than 7% except for N1 (67%) and N5 (18%). All nymph instars needed at least two feedings to molt (until six feedings for N5). The differentiation of a nymph into a female or a male could not be detected until the fifth instar for which the food intake was greater for a nymph developing into a female. Adults fed about once a week. The adult life span was around 400 days. The fecundity was 4.2 eggs/female/week, with a hatching rate of 50% and a hatching time of 39 days. In the same conditions, T. infestans showed a similar fecundity but a greater hatching rate and hatching time. A trial for rearing the adults at a higher temperature (26 °C) showed a drastic fall in the fecundity and in the hatching rate. The vectorial competence was analyzed for fifth instars and adults by three parameters: the ability to feed on human beings, the capacity to be infected by T. cruzi and the postfeeding defecation delay. Results showed a relatively high vectorial competence: (1) insects fed easily on the tested human being; (2) 100% of the specimens became infected by T. cruzi just by one infected meal; and (3) although the adults defecated after a median postfeeding delay greater than that of T. infestans, results on N5 suggest that they could be as good vectors as T. infestans males.     

Total pelvic mesh repair

INTRODUCTION: This report describes our technique and experience in restoring the pelvic floor of females with pelvic organ prolapse. METHODS: Total pelvic mesh repair uses a strip of Marlex Mesh® secured between the perineal body and the sacrum. Two additional strips, attached to the first, are tunneled laterally to the pubis and support the vagina and bladder laterally. Candidates for the procedure have failed previous standard repair or manifest combined organ prolapse on physical and cystodefecography exams. RESULTS: From January 1990 to December 1999, 236 females had total pelvic mesh repair, and 205 (87 percent) were available for follow-up. Median age was 64 (range, 32–89) years, median parity 2 (range, 1–9); 63 percent had birth-related complications. Bladder protrusion, vaginal protrusion, or both were the predominant chief complaint (54 percent), followed by anorectal protrusion (48 percent). Findings on physical examination showed degrees of prolapse of rectum (74 percent) and vagina (57 percent), perineal descent (63 percent), enterocele (47 percent), and rectocele (44 percent). Mean procedure time and length of hospital stay were 3.2 (standard deviation 0.75) hours and 6 (standard deviation 2.2) days, respectively. Reoperation rate because of complications of the total pelvic mesh repair procedure was 10 percent. Marlex® erosion into rectum or vagina occurred in 5 percent of patients and constituted 46 percent of the complications requiring reoperation. Additional surgical procedures at various intervals subsequent to total pelvic mesh repair have been performed in 36 percent of patients to further improve bladder function and have been performed in 28 percent of patients to improve anorectal function. There has been no recurrence of rectal or vaginal prolapse to date. Reports of overall satisfaction for correction of primary symptoms for patients grouped into early (0.5–3 years), middle (>3–6 years) and late (>6 years) were 68 percent, 73 percent, and 74 percent respectively. CONCLUSION: Total pelvic mesh repair is a safe and effective operation for females with pelvic organ prolapse.Presented at the meeting of the American Society of Colon and Rectal Surgeons, Boston, Massachusetts, June 24 to 29, 2000.     

Elektromyographisches aktivitätsverhalten des M. sphincter ani externus und M. puborectalis im defäkationstest bei patienten mit obstruktiven Entleerungsstörungen

Zusammenfassung In einer prospektiven elektromyographischen und manometrischen Studie wurde die Aktivität des M. sphincter ani externus und M. puborectalis bei Ruhe, Kontraktion und Pressen bei 23 Frauen (Durchschnittsalter 52 Jahre) mit obstruktiven Defäkationsstörungen untersucht. Als Kontrollgruppe dienten 22 gesunde Frauen mit einem durchschnittlichen Alter von 53 Jahren. In erster Linie sollte überprüft werden, wie die beiden Muskeln sich bei einer simulierten Defäkation (maximales Pressen) funktionell verhalten, und wie die Druckverhältnisse sich im Rektum und Analkanal dabei ändern. Ruhe-, Kontraktions- und Preßdruck (Rektum und Analkanal) zeigten zwischen den beiden Gruppen keine signifikanten Unterschiede. Puborectalis und Externus zeigten weitgehend sowohl in der Patienten- als auch in der Kontrollgruppe ein identisches Verhalten. Bis auf die Kontraktionsamplitude des M. puborectalis konnte man keine weitere statistischen Unterschiede zwischen den beiden Gruppen nachweisen. Beim Versuch, die veränderte Aktivität als Anismusindex zu erfassen, konnte eine solche Veränderung weder für den M. sphincter ani externus noch für den M. puborectalis objektiviert werden. Daraus folgern wir, daß eine elektromyographisch nachgewiesene Aktivitätszunahme der willkürlichen Beckenbodenmuskulatur während der Defäkation weniger eine pathologische Situation, sondern vielmehr einen Funktionszustand repräsentiert.

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Electromyographic activity of the external anal sphincter muscle and the puborectal muscle during the defecation test in patients with obstructive defecation disorder

In a prospective electromyographic and manometric study on 23 women (average age 52 years) with obstructive defecation disorder the activity of the external anal sphincter muscle and the puborectal muscle was investigated at rest and during contraction and straining. The control group consisted of 22 healthy women with an average age of 53 years. The main aim of the study was to investigate the functioning of the two muscles during simulated defecation (maximum strain) and to examine any changes in the pressure ratio in the rectum and the anal canal during this stimulation. There were no significant differences in the resting pressure, the contraction pressure and the straining pressure (in the rectum and the anal canal) between the two groups. The functioning of the puborectal muscle and the external anal sphincter muscle was largely the same in both the study group and the control group. No statistically significant differences were found between the two groups except in the amplitude of contraction. When we tried to list the change in the activity of the muscle as an index of anism, we were not able to objectify such a change for either the external anal sphincter muscle or the puborectal muscle. We therefore conclude that the increase in the activity of the voluntary muscle of the pelvic floor observed on electromyography during defecation does not indicate a pathologic condition but is a functional state.

     

Effects of zometapine, a structurally novel antidepressant, in an animal model of depression

Zometapine, a pyrazolodiazepine, bears a close structural resemblance to benzodiazepines. It possesses an unusual pharmacological profile, and is active in some, but not all, tests of antidepressant activity. In clinical tests it appears to be an extremely effective pharmacotherapeutic agent, and may represent a new class of antidepressant. Because the preclinical profile of zometapine is unusual, we examined its effects in a behavioral test of antidepressant potential. Following three weeks of treatment, the drug selectively reversed a behavioral depression following chronic stress. Drug-induced reversal was seen only in rats activated by acute noise exposure, and was dose related. Reversal was confirmed by a second measure, defecation, and partially confirmed by the normalization of an elevated basal corticosterone response.     

Effects of 5-hydroxytryptamine on defecation in open-field behavior in rats

An attempt was made to elucidate the role of the serotonergic nervous sytem in defecation resulting from environmental stimulation in rats. The open-field (OF) test and shuttle box method were used to study the defecation. 5-Hydroxytryptophan (5-HTP) significantly decreased the number of fecal boluses excreted in both emotional situations, namely, in both OF and shuttle box. The fecal excretion was significantly reduced compared with the controls after intraventricular injection of 5-hydroxytryptamine (5-HT). Animals pretreated with p-chlorophenylalanine (pCPA) and 5,6-dihydroxytryptamine (5,6-DHT) tended to show a slight increase in the OF defecation. 5-HTP was equally effective in diminishing the OF performance of pCPA-treated rats. The inhibitory effects of 5-HTP on the defecation were also observed after depletion of biogenic amines by reserpine treatment. Home cage defecation was increased after 5-HTP administration, decreased under pretreatment with pCPA and not influenced by intraventricular injection of 5-HTP. These results suggested that the defecation after environmental stimuli was due to a change in 5-HT levels in the brain.     

一种芦荟成分为主保健食品通便功效的动物试验研究

目的：评价以芦荟全叶冻干粉、小麦膳食纤维、苹果醋粉等为主要成分的保健食品通便功能。方法按卫生部《保健食品检验与评价技术规范》（2003年版）中润肠通便功能检验方法开展实验。经口给予小鼠3．0、1．0、0．5 g／kg体质量（相当人体推荐量的30、10、5倍）剂量的受试物15 d,采用不同剂量的复方地芬诺酯制备肠蠕动抑制模型和便秘模型。测定肠蠕动抑制模型小鼠小肠墨汁推进率、便秘小鼠排便时间、排粪便粒数和粪便重量。结果各剂量组小鼠各周体质量、体质量增加值未见明显变化;受试物低、中剂量组的小肠推进速度、第一粒黑便排出时间、6h排黑便粒数和黑便总重量与模型对照组比较变化不明显,差异无统计学意义（P＞0．05）;受试物高剂量组的小肠墨汁推进率和墨汁推进转换值则有明显增加,第一粒黑便排出时间提前,6 h排黑便粒数和黑便总重量有明显增加,与模型对照组比较,统计学分析差异有统计学意义（P＜0．05）。结论根据《保健食品检验与评价技术规范》（2003年版）,该受试物具有通便功能。     

新辅助放化疗对中低位直肠癌患者排便状况的影响

目的：探讨新辅助化疗对中低位直肠癌患者排便状况的影响。方法将单纯进行手术治疗的患者纳入对照组,新辅助放化疗结合手术治疗的患者纳入研究组。比较两种治疗方法对患者术后排便功能的影响。结果新辅助放疗组患者治疗前后肿瘤距齿状线距离存在显著差异,P＜0．05;两组患者治疗后排便异常存在显著差异,P＜0．05;年龄,行辅助放化疗和直肠癌根治术后吻合口距肛缘的距离是大便失禁发生率的影响因素,P＜0．05。结论新辅助放化疗对中低位直肠癌患者,能达到提高肿瘤切除率和提高保肛成功率的目的,虽然对术后患者排便功能有一定的影响,但是也不失为一种有效的治疗方法。