We have in a rat model studied the role of gastric neuroendocrine cells in the regulation of gastric function and growth and given indication for an important role of these cells in physiology and human carcinogenesis. Because of the high incidence of spontaneous tumors in the glandular stomach of mastomys (Praomys (mastomys) natalensis), we wanted to investigate if mastomys might be an useful model for our further studies.Tumors. were recognized in several organs of our mastomys, but not in the stomach. However, a high incidence oftrichobezoars was observed in the stomach and intestine, and obstruction from thesewas the cause of illness and death for many of them.Multiple factors are involved in the formation of bezoars. and these are discussed in relation to the occurrence in our mastomys colony

Hanssen, Ingolf

Waldum, Helge L

English

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Scand, J. Lab. Amm. Sci, No. 4 . 1993 . Vol 20Trichobezoars in praomys (mastomys) natalensisby IngtoHansxen and Helge L. WaldumDepartment ot'Ihboratory Animals and Department ochdicine,University Hospital. N-7006 Trondheitn Norway.IntroductionPraomys (mastomys) nastalensis, referred tohereafter as mastomys, is intermediated insize between the mouse and rat. It belongs tothe family Muridae as do the latter two spe-cies. The mastomys is found from the easternCape Province throughout Africa south ofthe Sahara and to Morocco in the far north—west. It was often called the multimammatemouse or ”African wild rodent” (Davies &081116 1958) which indicates that the specieshas only short history oflaboratory adaption.It was in South Africa in 1939 that initiationoflaboratory breeding from wild strains firstoccurred, and thereafter mastomys have beendistributed both to USA and Europe. Theoriginal scientific advantage ofmastomys wastheir high and uniform susceptibility to pla-gue and parasites (Saga & Saw 1978).High incidence of spontaneous tumors invarious organs and tissues have been rare inmammals other than mastomys (Saga & Saw1978) and man. For this reason the masto-mys has been the subject of oncological in-vestigations as a possible experimental ani»ma] mode] for human tumors. Tumors occurspontaneously rather frequently in the glan-dular stomach, liver, adrenal gland, thymus,pituitary gland, prostatae and ovary (Saga &Saw 1978). Several additional organs and tis—sues (kidneys, pancreas, seminal vesicles, te—sticles, and mammary glands) have also beenreported to produce tumors or tumor—like le-sions, though with a lower incidence (Hollan-der & Higgins 1971). We have in a rat modelduring several years studied the role of theneuroendocrine cells in the regulation ofgastric function and growth (Brenna & Wal-dum I991, Brenna e! a]. 1992), and givenindication for an important role of neuro-endocrine cells even in human gastric car—cinogenesis (Waldum er a]. 19913). The ma—stomys have the same distribution of gastriccells as in other mammals. and therefore wewanted to investigate if this species might bean useful model for our further studies.11!arena] and methodsTwelve adult pairs of mastomys were boughtfrom the Medical Research Council, ParkCrescent, London. Each pair was placed inseparate transparent plastic boxes (35x58x19cm) with a top cover of stainless netting andbottom covered by wood beddings (Beckay.GL-P). The animals were fed pelleted rat andmice feed (Ewes. 21 0/0 crude protein, 2.8 ”/0crude fibre) ad lib. and had also free access towater from water flasks. The room tempera-ture was about 22°C= the relative humidityabout 30—40 %, and the daylight regime 12 h.Infants were weaned three to four weeks post-partum.ResullsThe reproduction was low. During a periodof three years we got 76 adults from ourbreeding. Fifty-six animals were autopsied,either after being killed because of showingsigns of illness, or they were found dead.Twenty—five mastomys had trichobezoars,one to three in the stomach or duodenum.The bezoars were oblong and up to the size of1.6x0.8 cm, and obstruction from these wasthe cause of illness and death for many ma-stomys (Fig. 1). Tumors were recognized inthe accessory sex. glands, the lungs, kidneysand adrenals. but not in the stomach (Table1).DiscussionTrichobezoars are well known in cats, but arealso found in rabbits (Leary et al. 1984), feed—lot raised calves (Herd & Cook 1989) andcaptive nonhuman primates (Gil/in 0! al.225Scund. J. l.uh. Anim, Sci. No. 4. [993 . Vol. 20   O[figure I. Mastomys with trichobezoar filling upthe stomach and leading to obstruction and dilata-tion ot‘the oesophagus (arrow).Table I. The autopsy findings of 56 mastomys(Found dead or killed because of signs of illness). n = numberTrichobczoarsstomach7 duodenumli1vLuTumorsaccessory sex glandslungskidneysadrenals \O-—‘-—-OoOther findingsstomach bleedinguterus bleeding/dead during birthcannibalismdermatitisemaciation NWNLAN 2261990, Gozalo et a1. 1990). In human tricho—bezoars often are found in psychologically di-sturbed individuals. Over centuries thesebezoars have mainly been found in children.The classic pediatric case is that ofa partiallybalding child with a mass in the stomach(Jain er al. 1987). It is, however, also notedthat the incidence of bezoars in human pati-ents has increased as a result of operativemanipulation of the gastrointestinal tract(Ca/abuz'g at a]. 1989).The major complications of bezoars includeintestinal obstruction, gastric perforation, ga-stric ulcers and gastritis, and anorexia withweight loss (Calabuig el al. 1989). Intestinalobstmction results from the passage and sub-sequent lodging of a bezoar or part of a be-zoar in the distal small bowel. In human thiscomplication is most commonly seen in agastroectomized patient intact vagal nervesdue to the increased gastric outlet size with anundisturbed innervated gastric remnant. 1nthe individuals with vagectomized gastricremnants, the bezoar usually will remain inthe stomach leading to gastritis, gastric ulce—ration, and possible gastric perforation.Multiple factors are involved in the forma—tion of bezoars. Truncal vagotomy and theassociated gastric drainage operations resultsin diminished secretion and motility and areconsidered to play a major role (Calabuig eta]. 1989).Young cattle are particularly prone to bc-zoars, especially if deprived of dietary fibre(Jubb et al. 1985). Rabbits may also ingesttheir hair which accumulates in the stomachto form trichobezoars. Several antecedentfactors have been proposed to contribute tothe formation oftrichobezoars in this speciesincluding dietary deficiencies of roughage,copper, magnesium, protein. barrier housing,cage boredom, abnormal grooming, longhair, and an inability to vomit. A survey ofthe stomachs of208 healthy slaughter-rabbitsrevealed that 23.1 % had trichobezoars,which suggests that gastric trichobezoars arecommon in rabbits and that few animals withthese foreign bodies develop anorexia. Inaddition there appeared to he a high likeli—hood that trichobemars recur few weeks afterthey are operatively removed in rabbits (Le-aryel a]. 1984).Despite the literature about diseases in ma-stomys is extensive, trichobewars have notbeen described in this species. Our mastomyswere kept in a dry environment which mightbe the reason why some ofthem got conjunc—tivitis. ring—tail (Iglauer 81 al. 1993) anddry fur. This could have induced excessivegrooming (although it was not observed withcertainty). which could be the reason why somany got trichobezoars. It should. however.be recalled that ECL (enterochromaf‘fin like)cell derived tumors occur frequently in theseanimals (Hakansan at al. 1973), and thatECL cell hyperplasia in the rat induced redu-ced gastric emptying (Wa/dzmz m al. 1991b).Our mastomys were unfortunately not ex—amined for ECL cell hyperplasia but it mightbe a factor in the production ot‘bezoar in thisSpecies.SummaryWe have in a rat model studied the role ot‘gastricneuroendocrine cells in the regulation of gastricfunction and growth and given indication for animportant role of these cells in physiology andhuman carcinogenesis. Because 01. the high inci-dence of spontaneous tumors in the glandular sto»mach 0f mastomys (Praomys (mastomys) natalen-Sis), we wanted to investigate if mastomys might bean useful model for our furtherstudies.Tumors. were recogni7ed in :everal organs of ourmastomys, but not in the stomach. However, ahigh incidence oftrichobezoars was observed in thestomach and intestine, and obstruction from thesewas the cause 01‘ illness and death for many ofthem.Multiple factors are involved in the formation ofbezoars. and these are discussed in relation to theoccurrence in our mastomys colony.SammmzdragVi har 1 en mttemodel] undermkt de neuroendoekrine eellers rolle i reguleringen av magesekkensfunksjon og funnet indikasjoner for at disse cellenekan spille en viktig rolle ikke bare fysiologisk, menogsfi i den humane earcinogenese.Det er beskreyet hey forekomst av spontane svul-ster i magesekken hos mastomys (Praomys (masto-mys) natalensis), 0g vi ville derfor undersake omSeand. J. lab. A'iim Sci, \In. 4. 1993 V0110mastomys kunne vzerc en hrukbar modell i vareVidere studier. Det bte pavist spontane swlster 1Here forskjelhge organer hos vére mastomys. menikke i magesekken. lmidlertid fant vi 11‘1Ch0be703»rer i mag ckkcn 0g tat'men pa svaert mange dyr.Disse forarsakct obstruksjon som time til bade syk-dom og died.Mange forskjellige l‘aktorer cr invoivert i dannelsenav bezoarer. og disse er diskutert i relasjon til fore-komsten blant vine mastomys. l’lilt'enre/o / K. PelkonmiOlemme rottaa malhna kéytta'en tutkineet maha-Iaukun neuroendokriinisten solujen osuutta ma-halaukun toiminnan sééitelysséi ja kasvussa jasaaneet nayltiia' siitéi. etta niitéi on tfirlsefi 0511115fysiologiassaj karsinogeneesi 'h’ ihmisell'a‘. Halu-simme selyittfiéi voisiko moninisarotta mastomys011a k'a‘yttb'kelpoinen malli jatkotutkimuksiammevanen, koska sillfi esiintyy yleisesti spontaanejakasvaimia rauhasmahassa.Meidéin moninisiirotissamme loytyi kasvaimiamonista elimistéi. mutta ei mahalaukusta. Maha-laukussa ja suolistmsa esiintyi kuitenkin yleisestikarvapalloja ja naiden aiheuttama suolentukkeu-ma oh yleinen sairastumisen ja kuoleman aiheut-taja.Karvapellojen muodostumisocn vaikuttavat teki~jatja néiitéi pohditaan tassa' artikkelissa. RU/t’rum mb’rwma E & Ill. H'a/r/irm' Studies of isolatedparietal and enterochromaf‘fin-like cells fromthe rat. Scand. J. Gastroenterol. 1991, 26, 12954300.Brwmcz E. [IL Waldum. AK Sandwk. l? S(‘hll/Zt’Sagucii & A Kri.s'te/i.mz.' Effects on the ratoxyntic mucosa of the histamine 2-antagonistloxtidine and the H+. K+-ATPase inhibitoromeprazole. Aliment. Pharmacol. Ther. 1992,(’7, 335—349.(‘rtlabuig R, S Navarro. 1 Carrie, 1' Arligas. J.llnné.» & JP l.a(‘a/l«: Gastric emptying andbezoars. Am. J, Surg. I989. I57, 287—290.Dam DHA & AG Ocule: The multi-mammatemouse Rallus (Mastomys) natalensis. Smith:A laboratory adapted african wild rodent.Proc. Zool. Soc. (Lond.) 1958. 151, 293—299.Gil/in AG, AF Phipptzrd & .II" T/zon'zpsrm: Hare-wnorl W1. Waugh RC. Horvath JS. Gastric hae-morrhage and perforation caused by a trieho-bezoar in a baboon (Papio hamadryas). Lab.Anim. 1990.24.180—182.Gnmlo AS. E Montoya & TE Nolan: Trichobezoaars in two saddlcback tamarins (Saguinus fusci-collis). J. Med. Primatol. 1990,19, 151—153.Hm/ RM & LG Cuuk.‘ Hairbalts m feedlot-raisedcalves. Aust. Vet. J. 1986. 6/). 373—73.N N \4Scand. J. Lab. Anim. Sci. No. 4, 1993 . V01. 20Hollander 01‘ d2 J Higgi'nxon: Spontaneous can—cers in Praomys (mastomys) natalcnsis. J. Natl.Cancer.1nst. 1971.46, 1343—1355.Hfikonwn R, L-I Larsxon, C Oit'mann, KC Snell& F Sundler: Fluorescence and electron micro—scopic histochemistry of endocrine-like cells ingastric mucosa and aragyrophil tumor of Pra—omys (Mastomys) natalensis. Analysis of 5—hydroxytryptamine, histamine, histidine de-carboxylase, and aromatic amino acid decar—boxylase. Histochemie 1973. 37, 23—38.Iglatwr F, TSc-lilz'iter, S Holub & R Sachs: Ring»tail disorder observed in cotton rats (Sigmodonhispidus). Scand. J. Lab. Anim. Sci. 1993. 20,1 19—121.Jam K, S Chamania & JW Sabhanz’y: RecurrentTriehobezoar due to psychosocial stress. J. In-dian. Med. Assoc. 1987., 85, 363—364.Jubb K VF, PC Kenneth & N Palmer; Pathologyof domestic animals. 3rd ed. Orlanda, Fla.Academic Press 1985.228Leary SL, P] Manning & LC Anderson: Experi-mental and naturally-occurring gastric foreignbodies in laboratory rabbits. Lab. Animal, Sci.Baitimo l984,34,58$1.Saga J & H Sum: Praomys (mastomys) natalensis.The significance of their tumors and diseasesfor cancer research. Daiichi Printing Co, Ni-gataJapan 1978.VI'a/tlzm HL, 0A llaugen, C Isaksen, R. Mec‘sci &AK .S'andvilc.’ Are difuse gastric carcinomasneuroendocrinc tumours (ECL-omas)? Eur. J.Gastroenterol. Hepatol. 1991a, 3, 245—249.Wa/dum HL, T Lefty, 12' Brenna, AK Sandi'ik, llPetersen. B. SchulzeSflgnmz, S lionfi/s & MJMLewin.‘ Effect of the histamine—l antagonistastemizole alone or with omeprazole on ratgastric mucosa. Scand. J. Gastroenterol. 19911).26. 23—35.

Trichobezoars in praomys (mastomys) natalensis

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Trichobezoars in praomys (mastomys) natalensis

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