Radiological study of gastrointestinal motor activity after acute cisplatin in the rat. Temporal relationship with pica

Nausea and vomiting are amongst the most severe dose-limiting side effects of chemotherapy. Emetogenic activity in rats can only be evaluated by indirect markers, such as pica (kaolin intake), or delay in gastric emptying. The aim of this work was to study, by radiological methods, the alterations in gastrointestinal motility induced by acute cisplatin in the rat, and to compare them with the development of pica. Rats received cisplatin (0-6 mg kg(-1)) at day 0. In the pica study, individual food ingestion and kaolin intake were measured each day (from day -3 to day 3). In the radiological study, conscious rats received an intragastric dose of medium contrast 0, 24 or 48 h after cisplatin injection, and serial X-rays were taken 0-24 h after contrast. Cisplatin dose-dependently induced both gastric stasis and stomach distension, showing a strict temporal relationship with the induction of both acute and delayed pica. Radiological methods, which are non-invasive and preserve animals' welfare, are useful to study the effect of emetogenic drugs in the different gastrointestinal regions and might speed up the search for new anti-emetics.

WIN 55,212-2 prevents mechanical allodynia but not alterations in feeding behaviour induced by chronic cisplatin in the rat

Anorexia, nausea/emesis and peripheral sensorial neuropathy are frequent adverse effects associated with chemotherapy. Cannabinoids have been proposed to alleviate these effects, but their preventive properties in long-term experimental models have not been tested. This study was conducted to determine whether or not a cannabinoid agonist (WIN-55,212-2) can prevent anorexia, pica (an indirect marker of nausea in non-vomiting species, consisting of the ingestion of non-nutritive substances such as kaolin) and mechanical allodynia (a marker of peripheral neuropathy) induced by the antineoplastic drug cisplatin chronically administered. Isolated rats with free access to food and kaolin received either saline, cannabinoid vehicle, WIN-55,212-2 (1-2 mg kg(-1)), cisplatin (1-2 mg kg(-1)), or both drugs once per week for five consecutive weeks. Modifications in temperature, body weight gain, food and kaolin intake, and the threshold for mechanical allodynia were recorded. Additionally, the acute psychoactive effects of the cannabinoid (hypomotility, hypothermia, analgesia and catalepsia) were assayed by means of the cannabinoid tetrad. WIN 55,212-2 prevented the development of mechanical allodynia but not anorexia, pica and reduction in weight gain induced by chronic cisplatin. The effect of WIN 55,212-2 was evident even at a dose lacking activity in the cannabinoid tetrad. The preventive effect on cisplatin-induced mechanical allodynia exerted by the cannabinoid could be due to a neuroprotective role, as has been suggested for other conditions. The present results support the interest in the evaluation of cannabinoids for treatment of patients suffering or likely to suffer neuropathic pain.

Enteric neuropathy evoked by repeated cisplatin in the rat

BACKGROUND

Acute administration of the antitumoral drug cisplatin can induce nausea/emesis and diarrhea. The long-term effects of cisplatin on gastrointestinal motility, particularly after repeated administration, are not well known. Because cisplatin is highly neurotoxic, myenteric neurons can be affected. Our aim was to study the prolonged effects of repeated cisplatin administration in a rat model, focusing on gastrointestinal motor function and myenteric neurons.

METHODS

Rats received saline or cisplatin (1 or 3 mg kg(-1), i.p.) once weekly for 5 weeks. One week after treatment, both upper gastrointestinal transit and colonic activity were evaluated, and tissue samples from ileum, colon and rectum were processed for histological analysis. Intestinal transit was measured invasively (charcoal method). Colonic activity was determined electromyographically. The gut wall structure was evaluated in sections using conventional histology and immunohistochemistry. Whole-mount preparations from the distal colon were labeled for different markers, including nitric oxide synthase (NOS) and calcitonin-gene related peptide (CGRP) to determine relative proportions of myenteric neurons vs the total neuronal population labeled with HuC/D.

KEY RESULTS

One week after repeated cisplatin exposure, the upper gastrointestinal transit rate and colonic activity were dose-dependently reduced. The number of NSE- or HuC/D-immunoreactive myenteric neurons per ganglion was decreased; the proportion of CGRP-immunoreactive neurons was decreased, whereas that of NOS-immunoreactive cells was increased.

CONCLUSIONS & INFERENCES

Chronic cisplatin may induce an enteric neuropathy characterized by changes in myenteric neurons associated with marked gastrointestinal motor dysfunction.

Cisplatin-induced gastrointestinal dysmotility is aggravated after chronic administration in the rat. Comparison with pica

BACKGROUND

Chemotherapy induces nausea/emesis and gastrointestinal dysmotility. Pica, the ingestion of non-nutritive substances, is considered as an indirect marker of nausea/emesis in non-vomiting species, like the rat. Cisplatin is the most emetogenic antitumoral drug. In the rat, acute cisplatin induces pica and gastric dysmotility in a temporally related manner, but the effects of chronic cisplatin are not well known. This study analyzed the effects of chronic cisplatin on pica and on gastrointestinal motor function in the rat, using radiographic, non-invasive methods.

METHODS

Rats received saline or cisplatin (1-3 mg kg(-1), i.p.) once a week for four consecutive weeks. Serial X-rays were taken 0-8 h after administration of barium sulfate, which was given intragastrically immediately after the first and last cisplatin administrations and 1 week after treatment finalization. Pica (i.e., kaolin intake) was measured in isolated rats.

KEY RESULTS

Cisplatin delayed gastric emptying and induced acute (during the 24 h following each administration) pica. Upon chronic administration, these effects were exacerbated. In addition, basal kaolin intake was enhanced (facilitated) and gastric distension induced. Delayed gastric emptying and gastric distension were not apparent 1 week after treatment, but basal kaolin intake was still elevated.

CONCLUSIONS & INFERENCES

Whereas gastric dysmotility induced by cisplatin is parallel to the development of acute pica and might underlie facilitation of pica throughout chronic treatment, it does not explain its long-term maintenance. These findings should be taken into account in the search for new antiemetic strategies.

Characterization of cannabinoid-induced relief of neuropathic pain in a rat model of cisplatin-induced neuropathy

Clinical use of antineoplastic drugs is associated with the development of numerous adverse effects that many patients find intolerable, including peripheral neuropathy. Cannabinoids have relieved neuropathic pain in different animal models. But their therapeutic activities could be affected by their psychoactive properties. The aim of this work was to determine the effect of cannabinoids in cisplatin-evoked neuropathy. For this purpose, the non-selective agonist WIN 55,212-2 (WIN), the CB1-selective agonist ACEA or the CB2-selective agonist JWH133 (or their vehicle) was either systemically administered at a non-psychoactive dose or locally injected in cisplatin-treated rats. Selective CB1 and CB2 cannabinoid antagonists (AM251 and SR144528, respectively) were used to characterize cannabinoid effects. Cisplatin-treated rats showed mechanical allodynia but not thermal hyperalgesia. Cannabinoid agonists alleviated mechanical allodynia. This effect was mediated by both CB1 and CB2 cannabinoid receptors when the cannabinoid was systemically applied. At the dose used, cannabinoid agonists had no psychoactive effect. The local effect of the drug involved the activation of peripheral CB1 receptors whereas involvement of CB2 receptors was less clear. In a rat model of cisplatin-induced neuropathy, cannabinoids have an antinociceptive effect, but the cannabinoid receptors involved could be different depending on the route of administration. Non-psychoactive doses of cannabinoid agonists are capable of alleviating the signs of peripheral neuropathy when systemically applied. Interestingly, local administration of selective CB1 agonists or systemic administration of CB2 agonists, which are non-psychoactive, may serve as new therapeutic alternatives for symptom management in painful neuropathy associated with cisplatin treatment.

Altered feeding behaviour induced by long-term cisplatin in rats

In animals without the emetic reflex, several emetogenic stimuli induce pica, an altered feeding behaviour consisting of the ingestion of non-nutritive substances. The development of pica in response to an emetogenic stimulus has been proposed to be useful as an indirect marker of nausea in the rat. In fact, like nausea and emesis in humans, it is accompanied by serotonin release from the enterochromaffin cells, increased c-fos labelling in the area postrema and the nucleus tractus solitarius, and a delay in gastric emptying. Furthermore, pica, measured as kaolin intake, is reduced by anti-emetic drugs. Pica has been demonstrated after single doses of cisplatin, the most emetogenic chemotherapeutic drug. However, cisplatin, as other antineoplastic drugs, is generally given in cycles, where conventional anti-emetics tend to lose efficiency. The aim of this work was to evaluate the pica induced by long-term treatment with cisplatin. Saline or cisplatin was administered once a week for 5 consecutive weeks, and temperature, body weight, food ingestion and kaolin intake were measured on a daily basis. The influence of isolation (pica is necessarily studied in isolated animals) and exposure to kaolin (basal kaolin intake could modify pica itself and other parameters) on temperature, body weight and daily food ingestion was negligible in saline-treated rats. Cisplatin administered at 3 mg/kg/week was too toxic: it produced hypothermia, weight drop and anorexia in both grouped and isolated rats, and 50% mortality in isolated animals. Toxicity associated with cisplatin administered at 1 mg/kg/week was acceptable, with a slower rate of weight gain being the major effect. In these rats, each cisplatin injection produced both acute anorexia and rebound hyperphagic responses. In addition, each administration induced both acute pica and an increase in basal kaolin intake, resembling the development of nausea in humans. This model could be useful for studying both the mechanisms leading to nausea associated with a long-term antineoplastic treatment and the efficiency of new anti-emetic drugs.

A comparison between an in vitro method to determine carbohydrate digestion rate and the glycemic response in young men

OBJECTIVE

This study examines the relationship between the results of in vitro determinations of carbohydrate digestion rates and the glycemic index.

SUBJECTS

Ten healthy non smoking men, aged between 21 and 24-y-old, were selected to participate in the study.

METHODS

Six different meals with similar levels of carbohydrates were assayed at breakfast in ten subjects and blood samples were obtained at 0, 15, 30, 60 and 120 min to determine glucose levels. The Englyst's enzymatic method was used in the in vitro study. The six meals were based in cereals (rice or spaghetti); legumes (lentil soup and beans with spaghetti); and potato (potato stew with meat and vegetables).

RESULTS

The meals showed different glycemic indices: rice and spaghetti based meals had lower values (mean value 31.4 and 42, respectively); the intermediate values corresponded to lentil soup and the bean dish (49.3, and 76.8 respectively) and the higher glycemic index was shown by the potato based meal (82).

CONCLUSIONS

A significant correlation was observed when the ratio of rapid carbohydrate digestion rate and the lente carbohydrate digestion rate was correlated with the glycemic index of the meals, but not when only the rapid carbohydrate digestion rate was considered. These results demonstrate a useful, simple and inexpensive method to estimate the biological response of high carbohydrate meals.

Cannabinoid/agonist WIN 55,212-2 reduces cardiac ischaemia–reperfusion injury in Zucker diabetic fatty rats: role of CB2 receptors and iNOS/eNOS

BACKGROUND

Diabetes increases cardiac damage after myocardial ischaemia. Cannabinoids can protect against myocardial ischaemia/reperfusion injury. The aim of this study was to examine the cardioprotective effect of the cannabinoid agonist WIN 55,212-2 (WIN) against ischaemia/reperfusion injury in an experimental model of type 2 diabetes. We performed these experiments in the Zucker diabetic fatty rat, and focused on the role of cannabinoid receptors in modulation of cardiac inducible nitric oxide synthase (iNOS)/endothelial-type nitric oxide synthase (eNOS) expression.

METHODS

Male 20-week-old Zucker diabetic fatty rats were treated with vehicle, WIN, the selective CB1 or CB2 receptor antagonists AM251 and AM630, respectively, AM251 + WIN or AM630 + WIN. Hearts were isolated from these rats, and the cardiac functional response to ischaemia/reperfusion injury was evaluated. In addition, cardiac iNOS and eNOS expression were determined by western blot.

RESULTS

WIN significantly improved cardiac recovery after ischaemia/ reperfusion in the hearts from Zucker diabetic fatty rats by restoring coronary perfusion pressure and heart rate to preischaemic levels. Additionally, WIN decreased cardiac iNOS expression and increased eNOS expression after ischaemia/reperfusion in diabetic hearts. WIN-induced cardiac functional recovery was completely blocked by the CB2 antagonist AM630. However, changes in NOS isoenzyme expression were not affected by the CB antagonists.

CONCLUSIONS

This study shows a cardioprotective effect of a cannabinoid agonist on ischaemia/reperfusion injury in an experimental model of a metabolic disorder. The activation mainly of CB2 receptors and the restoration of iNOS/eNOS cardiac equilibrium are mechanisms involved in this protective effect. These initial studies have provided the basis for future research in this field.

Ileal myenteric plexus in aged guinea-pigs: loss of structure and calretinin-immunoreactive neurones

Myenteric plexus controls gastrointestinal motility by means of well organized circuits which are comprised of sensory neurones, interneurones and motor neurones to the muscular layers. Calretinin (CR) is a calcium-binding protein that, in guinea-pig ileum, has only been found in ascending interneurones, which also express neurofilament triplet proteins (NFT), and excitatory longitudinal muscle motor neurones, which do not. In spite of some evidence that age affects both function and structure of the myenteric plexus, little is known about the possible selectivity of the process regarding specific myenteric neuronal phenotypes. The influence of age on both the structure of the myenteric plexus and the presence of CR-immunoreactive (CR-IR) neurones was studied using conventional immunohistochemical procedures applied to ileal whole-mount preparations from guinea-pigs. Both a reduction in ganglionic size and changes in the distribution of neurones inside and outside the ganglia, together with a general neuronal loss were found in preparations from aged guinea-pigs. More interestingly, a relatively more pronounced age-related loss of CR-IR neurones, especially those lacking of NFT expression, was found. Specific myenteric neuronal phenotypes may show differential sensitivity to ageing, and this could, under certain circumstances, alter the functional balance of gastrointestinal motility in aged individuals.

Characterization of cannabinoid-induced relief of neuropathic pain in rat models of type 1 and type 2 diabetes

Diabetic neuropathy is a frequent complication of diabetes mellitus with a tremendous impact on patients' quality of life, and it remains poorly treated. Cannabinoids relieve the signs of diabetic neuropathy in different experimental models, including streptozotocin- (STZ-) induced type 1 diabetic rodents, and they may also relieve neuropathic signs in type 2 diabetic animals. This study compares the effect of the non-selective cannabinoid agonist WIN 55,212-2 (WIN) in Zucker Diabetic Fatty (ZDF) rats (type 2 diabetes) and in STZ-injected Wistar rats (type 1 diabetes). WIN (or its vehicle) was either systemically administered at a non-psychoactive dose or locally injected. Selective CB1 and CB2 cannabinoid antagonists were used to characterize WIN antineuropathic effects. Both type 1 and type 2 diabetic rats showed mechanical allodynia but not thermal hyperalgesia. WIN alleviated mechanical allodynia in both models of diabetes. In STZ-treated rats, both cannabinoid receptors were involved, whereas in ZDF rats, WIN effects seemed to mainly involve the activation of CB1 receptors. Higher doses of WIN were needed to significantly relieve mechanical allodynia upon intraplantar administration in ZDF vs. STZ-injected rats. Cannabinoids, acting on systemic and/or peripheral receptors, may serve as a new therapeutic alternative for symptom management in painful neuropathy associated with both type 1 and type 2 diabetes. Additionally, our results highlight the need for appropriate selection of diabetic experimental models because the results from studies in STZ-induced diabetic rodents might not be applicable in all diabetic situations.

Advances in the purification of the mitochondrial Ca2+ uniporter using the labeled inhibitor 103Ru360

For many years the calcium uniporter has eluded attempts of purification, partly because of the difficulties inherent in the purification of low-abundance hydrophobic proteins (Reed and Bygrave, 1974). Liquid-phase preparative isoelectric focusing improved the fractionation of mitochondrial membrane proteins. A single 6-h run resulted in a 90-fold increase in specific activity of pooled active fractions over a semipurified fraction, allowing for enrichment of the calcium transport function in cytochrome oxidase vesicles. An additional powerful tool in the isolation of the uniporter was the use of the labeled inhibitor 103Ru360 as an affinity ligand; by following this procedure a protein of 18 kDa was purified in nondenatured, but rather inactive, form. The labeled protein corresponds to the protein that showed Ca2+ transport activity.

Selective lack of tolerance to delayed gastric emptying after daily administration of WIN 55,212-2 in the rat

The use of cannabinoids to treat gastrointestinal (GI) motor disorders has considerable potential. However, it is not clear if tolerance to their actions develops peripherally, as it does centrally. The aim of this study was to examine the chronic effects of the cannabinoid agonist WIN 55,212-2 (WIN) on GI motility, as well as those in the central nervous and cardiovascular systems. WIN was administered for 14 days, at either non-psychoactive or psychoactive doses. Cardiovascular parameters were measured in anaesthetized rats, whereas central effects and alterations in GI motor function were assessed in conscious animals using the cannabinoid tetrad and non-invasive radiographic methods, respectively. Tests were performed after first (acute effects) and last (chronic effects) administration of WIN, and 1 week after discontinuing treatment (residual effects). Food intake and body weight were also recorded throughout treatment. Blood pressure and heart rate remained unchanged after acute or chronic administration of WIN. Central activity and GI motility were acutely depressed at psychoactive doses, whereas non-psychoactive doses only slightly reduced intestinal transit. Most effects were reduced after the last administration. However, delayed gastric emptying was not and could, at least partially, account for a concomitant reduction in food intake and body weight gain. The remaining effects of WIN administration in GI motility were blocked by the CB1 antagonist AM 251, which slightly accelerated motility when administered alone. No residual effects were found 1 week after discontinuing cannabinoid treatment. The different systems show differential sensitivity to cannabinoids and tolerance developed at different rates, with delayed gastric emptying being particularly resistant to attenuation upon chronic treatment.

Cannabinoid-induced delayed gastric emptying is selectively increased upon intermittent administration in the rat: role of CB1 receptors

BACKGROUND

Cannabinoids acutely administered depress central, cardiovascular and gastrointestinal functions. These effects might be modified upon repeated administration. Compared to the effects induced by daily administration, those induced by intermittent administration are less known. The effect of intermittent treatment with the CB1/CB2 cannabinoid agonist WIN55,212-2 (WIN) was studied in the rat.

METHODS

Male rats received saline, vehicle or WIN at 0.5 (low-WIN) or 5 (high-WIN) mg kg(-1) week(-1) for 4 weeks. WIN effects on the central nervous system (cannabinoid tetrad tests), cardiovascular function and gastrointestinal motor function were evaluated after the first and last doses, and, where appropriate, 1 week after the last dose. To determine the involvement of CB1 receptors in the chronic effect of WIN, the CB1 receptor antagonist/inverse agonist AM251 (1 mg kg(-1)) was used.

KEY RESULTS

High- (but not low-) WIN induced the four signs of the cannabinoid tetrad, and reduced gastrointestinal motility, but did not alter cardiovascular parameters. Upon chronic intermittent administration, tolerance did not clearly develop to WIN effects. Quite the opposite, depression of gastric emptying was intensified. No effect was long-lasting. Repeated administration of AM251 was more efficacious than single administration to block WIN chronic central effects, but the opposite occurred regarding lower intestinal motility.

CONCLUSIONS & INFERENCES

Upon intermittent administration, hypersensitization may develop to some effects (particularly delayed gastric emptying) induced by cannabinoid agonists. CB1 antagonists/inverse agonists may show different efficacy upon repeated or single administration to block cannabinoid-induced central and gastrointestinal effects. Thus, cannabinoid effects are dependent on the pattern of drug administration.

May cannabinoids prevent the development of chemotherapy-induced diarrhea and intestinal mucositis? Experimental study in the rat

BACKGROUND

The antineoplastic drug 5-fluoruracil (5-FU) is a pirimidine analog, which frequently induces potentially fatal diarrhea and mucositis. Cannabinoids reduce gastrointestinal motility and secretion and might prevent 5-FU-induced gut adverse effects. Here, we asked whether cannabinoids may prevent diarrhea and mucositis induced by 5-FU in the rat.

METHODS

Male Wistar rats received vehicle or the non-selective cannabinoid agonist WIN 55,212-2 (WIN; 0.5 mg kg^-1 injection^-1 , 1 injection day^-1 , 4 consecutive days) by intraperitoneal (ip) route; on the first 2 days, animals received also saline or 5-FU (150 mg kg^-1 injection^-1 , cumulative dose of 300 mg kg^-1 ). Gastrointestinal motor function was radiographically studied after barium contrast intragastric administration on experimental days 1 and 4. Structural alterations of the stomach, small intestine and colon were histologically studied on day 4. PAS staining and immunohistochemistry for Ki67, chromogranin A and CD163 were used to detect secretory, proliferating, and endocrine cells, and activated macrophages respectively.

KEY RESULTS

As shown radiographically, 5-FU induced significant gastric emptying delay (on days 1 and 4) and diarrhea (on day 4). WIN did not significantly alter the motility curves obtained for either control or 5-FU-treated animals but tended to reduce the severity of 5-FU-induced diarrhea and increased permanence of barium from day 1 to the beginning of day 4 in 5-FU-treated animals. 5-FU-induced mucositis was severe and not counteracted by WIN.

CONCLUSIONS AND INFERENCES

5-FU-induced diarrhea, but not mucositis, was partly prevented by WIN at a low dose. Cannabinoids might be useful to prevent chemotherapy-induced diarrhea.

In vitro and non-invasive in vivo effects of the cannabinoid-1 receptor agonist AM841 on gastrointestinal motor function in the rat

BACKGROUND

Cannabinoids have been traditionally used for the treatment of gastrointestinal (GI) symptoms, but the associated central effects, through cannabinoid-1 receptors (CB1R), constitute an important drawback. Our aims were to characterize the effects of the recently developed highly potent long-acting megagonist AM841 on GI motor function and to determine its central effects in rats.

METHODS

Male Wistar rats were used for in vitro and in vivo studies. The effect of AM841 was tested on electrically induced twitch contractions of GI preparations (in vitro) and on GI motility measured radiographically after contrast administration (in vivo). Central effects of AM841 were evaluated using the cannabinoid tetrad. The non-selective cannabinoid agonist WIN 55,212-2 (WIN) was used for comparison. The CB1R (AM251) and CB2R (AM630) antagonists were used to characterize cannabinoid receptor-mediated effects of AM841.

KEY RESULTS

AM841 dose-dependently reduced in vitro contractile activity of rat GI preparations via CB1R, but not CB2R or opioid receptors. In vivo, AM841 acutely and potently reduced gastric emptying and intestinal transit in a dose-dependent and AM251-sensitive manner. The in vivo GI effects of AM841 at 0.1 mg/kg were comparable to those induced by WIN at 5 mg/kg. However, at this dose, AM841 did not induce any sign of the cannabinoid tetrad, whereas WIN induced significant central effects.

CONCLUSIONS & INFERENCES

The CB1R megagonist AM841 may potently depress GI motor function in the absence of central effects. This effect may be mediated peripherally and may be useful in the treatment of GI motility disorders.

Pepsin egg white hydrolysate ameliorates metabolic syndrome in high-fat/high-dextrose fed rats

The aim of this study was to examine the effect of a pepsin egg white hydrolysate (EWH) on metabolic complications using a high-fat/high-dextrose diet-induced Metabolic Syndrome (MetS) experimental model. Male Wistar rats were divided into 4 groups which received: standard diet and water (C), standard diet and a solution with 1 g kg^-1 day^-1 of EWH (CH), high-fat/high-dextrose diet and water (MS), and high-fat/high-dextrose diet and a solution with 1 g kg^-1 day^-1 of EWH (MSH). EWH consumption normalized body weight gain; abdominal obesity and peripheral neuropathy developed in MetS animals, and adipose tissue and liver weight, as well as plasma glucose were reduced. Oxidative stress and inflammation biomarkers were normalized in MSH animals. In conclusion, the oral administration of EWH could be used as a functional food ingredient to improve some complications associated with MetS induced by unhealthy diets.

Mitochondrial permeability transition as induced by cross-linking of the adenine nucleotide translocase

Mitochondrial permeability transition is caused by the opening of a transmembrane pore whose chemical nature has not been well established yet. The present work was aimed to further contribute to the knowledge of the membrane entity comprised in the formation of the non-specific channel. The increased permeability was established by analyzing the inability of rat kidney mitochondria to take up and accumulate Ca2+, as well as their failure to build up a transmembrane potential, after the cross-linking of membrane proteins by copper plus ortho-phenanthroline. To identify the cross-linked proteins, polyacrylamide gel electrophoresis was performed. The results are representative of at least three separate experiments. It is indicated that 30 microM Cu2+ induced the release of 4.3 nmol Ca2+ per mg protein. However, in the presence of 100 microM ortho-phenanthroline only 2 microM Cu2+ was required to attain the total release of the accumulated Ca2+; it should be noted that such a reaction is not inhibited by cyclosporin. The increased permeability corresponds to cross-linking of membrane proteins in which approximately 4 nmol thiol groups per mg protein appear to be involved. Such a linking process is inhibited by carboxyatractyloside. By using the fluorescent probe eosin-5-maleimide the label was found in a cross-linking 60 kDa dimer of two 30 kDa monomers. From the data presented it is concluded that copper-o-phenanthroline induces the intermolecular cross-linking of the adenine nucleotide translocase which in turn is converted to non-specific pore.

Alterations in the small intestinal wall and motor function after repeated cisplatin in rat

BACKGROUND

Gastrointestinal adverse effects occurring during cancer chemotherapy are well known and feared; those persisting once treatment has finished are relatively unknown. We characterized the alterations occurring in the rat small intestine, after repeated treatment with cisplatin.

METHODS

Male Wistar rats received saline or cisplatin (2 mg kg^-1  week^-1 , for 5 weeks, ip). Gastric motor function was studied non-invasively throughout treatment (W1-W5) and 1 week after treatment finalization (W6). During W6, upper gastrointestinal motility was also invasively studied and small intestinal samples were collected for histopathological and molecular studies. Structural alterations in the small intestinal wall, mucosa, submucosa, muscle layers, and lymphocytic nodules were histologically studied. Periodic acid-Schiff staining and immunohistochemistry for Ki-67, chromogranin A, and neuronal-specific enolase were used to detect secretory, proliferating, endocrine and neural cells, respectively. The expression of different markers in the tunica muscularis was analyzed by RT/qPCR.

KEY RESULTS

Repeated cisplatin induced motility alterations during and after treatment. After treatment (W6), the small intestinal wall showed histopathological alterations in most parameters measured, including a reduction in the thickness of circular and longitudinal muscle layers. Expression of c-KIT (for interstitial cells of Cajal), nNOS (for inhibitory motor neurons), pChAT, and cChAT (for excitatory motor neurons) increased significantly (although both ChATs to a lesser extent).

CONCLUSIONS & INFERENCES

Repeated cisplatin induces relatively long-lasting gut dysmotility in rat associated with important histopathological and molecular alterations in the small intestinal wall. In cancer survivors, the possible chemotherapy-induced histopathological, molecular, and functional intestinal sequelae should be evaluated.

Cannabinoids may worsen gastric dysmotility induced by chronic cisplatin in the rat

BACKGROUND

Although cannabinoids have traditionally been used for the treatment and/or prevention of nausea and/or emesis, anorexia and weight loss induced by clinical use of antineoplastic drugs, their efficacy and safety in long-term treatments are still controversial. Our aim was to analyze the effects of the non-selective cannabinoid agonist WIN 55 212-2 (WIN) on gastrointestinal (GI) dysmotility and other adverse effects induced by repeated cisplatin administration in the rat.

METHODS

Male Wistar rats received two intraperitoneal injections once a week for 4 weeks: the first one was WIN, at non-psychoactive doses (0.5 or 1 mg kg(-1)), its vehicle or saline; the second one was cisplatin (2 mg kg(-1)) or saline. Radiographic techniques were used to determine the acute (after first dose), chronic (after last dose), and residual (1 week after treatment finalization) effects of cisplatin and/or WIN on GI motility. Bodyweight gain, food ingestion, and mechanical sensitivity were also tested.

KEY RESULTS

Weekly cisplatin induced mechanical allodynia, which WIN prevented, as well as weight gain reduction and anorexia, which WIN did not. Gastric emptying was dose-dependently delayed by cisplatin and this effect was enhanced upon chronic treatment. WIN aggravated cisplatin-induced gastric dysmotility. One week after treatment finalization, only minor alterations of GI motor function were found in rats treated with cisplatin, WIN or both.

CONCLUSIONS & INFERENCES

WIN weekly administered at low doses prevents neuropathy, but does not prevent anorexia or weight loss and aggravates gastric dysmotility induced by cisplatin. Cannabinoids should be handled with caution if chronically administered during chemotherapy.

Mycobacterium fortuitum peritonitis in two patients receiving continuous ambulatory peritoneal dialysis

We present two cases of non-resolving peritonitis treated with a standard peritonitis protocol. The organism identified from the peritoneal effluent was Mycobacterium fortuitum, a group IV (Runyon's classification) rapidly growing, nontuberculous mycobacterium. M. fortuitum is ubiquitous and can be isolated from a number of natural sources. Risk factors these two patients had for developing M. fortuitum peritonitis included underdialysis, the immunocompromised state associated with end stage renal disease, prior or prolonged broad spectrum antibiotic treatment, and possible exposure to environmental factors, since both were hospitalized at about the same time. The isolates were resistant to the conventional antibiotics recommended for the treatment of this mycobacterium. Both patients, however, responded to catheter removal and antibiotics administered according to the sensitivities of the mycobacterium isolated.

Short-term satiety in preschool children: a comparison between high protein meal and a high complex carbohydrate meal

The aim of this study was to investigate whether a high protein meal has a different effect on short-term satiety in preschool children than a high carbohydrate meal by measuring their intake of a subsequent meal. Subjects were 35 normal preschool children of both genders aged 5 to 6 years. All children were healthy and randomly chosen from those who were attending to a day-care center where they received feeding at three meal times: breakfast, lunch and teatime. Children were weighed with light clothes following standard recommendations. They were normal according to the weight for height index, using the NCHS standards. Two meals with different levels of protein and carbohydrate and equal energy contents were assayed at lunch. The lunches were cooked dishes made from common ingredients. The high carbohydrate meal was consumed in greater amount than the high protein meal (P < 0.01) and a significantly greater energy intake was observed (P < 0.01). Food and energy intakes at teatime were greater with the high carbohydrate meal, but only the energy intake was significant (P < 0.05). When subjects consumed the high protein meal during lunch, they ate a significantly lower amount of protein in the subsequent meal, but the carbohydrate intake was similar. The long-term effects of a high protein diet remain to be investigated before recommending of a high protein for obese children.

Preclinical evaluation of the effects on the gastrointestinal tract of the antineoplastic drug vincristine repeatedly administered to rats

BACKGROUND

Vincristine is a commonly used chemotherapeutic agent. It is associated with undesirable digestive side effects. However, the impact of vincristine on gastrointestinal structure and motility or its long-term effects have not been deeply studied in animal models. This could be useful in order to develop therapeutic or preventive strategies for cancer patients. The aim of this study was to analyze such effects.

METHODS

Rats received saline or vincristine (0.1 mg kg^-1 , ip) daily for 10 days. Evaluations were performed during treatment and 2-6 weeks after. Somatic mechano-sensitivity was assessed using von Frey hairs. Gastrointestinal motor function was studied by means of radiographic still images and colonic propulsion of fecal pellets using fluoroscopy videos. Histological assessment of the gut morphology and immunohistochemistry for HuC/D and nNOS were performed in whole-mount myenteric plexus preparations.

KEY RESULTS

Peripheral sensitivity was increased in animals treated with vincristine and did not subside 2 weeks after treatment finalization. Vincristine treatment inhibited gastrointestinal motility although this was recovered to normal values with time. Damage in the digestive wall after vincristine treatment was greater in the ileum than in the colon. Villi shortening (in ileum) and large inflammatory nodules still remained 2 weeks after treatment finalization. Finally, the proportion of nNOS-immunoreactive neurons was increased with vincristine and continued to be increased 2 weeks after treatment finalization.

CONCLUSIONS AND INFERENCES

Vincristine alters gastrointestinal motility, peripheral sensitivity and mucosal architecture. Vincristine-induced neuropathy (somatic and enteric), intestinal mucosa damage and inflammatory infiltrations are relatively long-lasting.

Age-related changes in the gastrointestinal tract: a functional and immunohistochemical study in guinea-pig ileum

It is known that there is an age-related increase in gastrointestinal diseases. However, there is a lack of studies dealing with the correlation between age-related changes in function and intrinsic innervation in the gastrointestinal tract. The purpose of this work was to study this subject in the guinea pig ileum, whose functional and structural features are well known in the young age. Ileal longitudinal muscle -- myenteric plexus (LMMP) preparations were obtained from 3-to 24-month-old guinea pigs. Both functional and immunohistochemical techniques were applied. The force of the contraction elicited by excitatory stimuli (electrical stimulation, acetylcholine, substance P, and opioid withdrawal) increased in parallel with an age-dependent reduction in the density of excitatory motor neurones to the longitudinal muscle, whereas other subpopulations of neurones, including inhibitory motor neurones, decreased much more slowly. Although the increase in responsiveness could be related to the age/weight-related increment in muscle bulk, some compensatory modifications to the lowered density of excitatory neurones could also be involved. On the other hand, the acute inhibitory response to morphine remained unaltered in old animals, whilst in vitro tolerance was lower. These results suggest that although age-dependent neuronal loss does not cause dramatic changes in intestinal motility, it is a factor that could contribute to disturbing normal responsiveness and, perhaps, underlie the higher frequency of gastrointestinal diseases encountered in the elderly.