Histochemical study on the neuro-insular complex in Suncus murinus.

Ganglia, rich in cholinesterase substance, were recorded at a little distance to the islets of Langerhans, connected with the fibres of the peri-insular plexus which were referred as neuro-insular complex. The peri-insular complex was made up of a large number of non-myelinated and partially by myelinated nerve fibres, and it was found in association with the post-ganglionic nerve fibres.     

Interdigestive migrating contractions are coregulated by ghrelin and motilin in conscious dogs

During fasting, gastrointestinal (GI) motility is characterized by cyclical motor contractions. These contractions have been referred to as interdigestive migrating contractions (IMCs). In dogs and humans, IMCs are known to be regulated by motilin. However, in rats and mice, IMCs are regulated by ghrelin. It is not clear how these peptides influence each other in vivo. The aim of the present study was to investigate the relationship between ghrelin and motilin in conscious dogs. Twenty healthy beagles were used in this study. Force transducers were implanted in the stomach, duodenum, and jejunum to monitor GI motility. Subsequent GI motility was recorded and quantified by calculating the motility index. In examination 1, blood samples were collected in the interdigestive state, and levels of plasma ghrelin and motilin were measured. Plasma motilin peaks were observed during every gastric phase III, and plasma ghrelin peaks occurred in nearly every early phase I. Plasma motilin and ghrelin levels increased and decreased cyclically with the interdigestive states. In examination 2, saline or canine ghrelin was administered intravenously during phase II and phase III. After injection of ghrelin, plasma motilin levels were measured. Ghrelin injection during phases II and III inhibited phase III contractions and decreased plasma motilin levels. In examination 3, ghrelin was infused in the presence of the growth hormone secretagogue receptors antagonist [D-Lys3]-GHRP-6. Continuous ghrelin infusion suppressed motilin release, an effect abrogated by the infusion of [D-Lys3]-GHRP-6. Examination 4 was performed to evaluate the plasma ghrelin response to motilin administration. Motilin infusion immediately decreased ghrelin levels. In this study, we demonstrated that motilin and ghrelin cooperatively control the function of gastric IMCs in conscious dogs. Our findings suggest that ghrelin regulates the function and release of motilin and that motilin may also regulate ghrelin.     

5-羟色胺和胃动素在狗小肠移行性复合运动调控中的作用

应用慢性植入小肠腔外应力传感器记录清醒狗小肠移行性复合运动（ＭＭＣ）。在颈外静脉和支配１０￣１５ｃｍ肠段的空肠动脉内分别放置－硅胶管以备灌流药物的取血样品用。本研究观察了静脉和动脉注射药物对小肠ＭＭＣ的影响及ＭＭＣ不同时相血浆５－羟色胺（５－ＨＴ）和胃动素的浓度变化。结果表明：（１）ＭＭＣ不同时相血浆５－ＨＴ和胃动素浓度呈周期性变化,５－ＨＴ峰值在胃动素峰值之前出现。血浆５－ＨＴ浓度在ＭＭＣⅡ相后     

Ghrelin, des-acyl ghrelin and obestatin on the gastrointestinal motility

Ghrelin, des-acyl ghrelin and obestatin are derived from a common prohormone, preproghrelin by posttranslational processing, originating from endocrine cells in the stomach. Ghrelin exerts stimulatory effects on the motility of antrum and duodenum in both fed and fasted state of animals. On the other hand, des-acyl ghrelin exerts inhibitory effects on the motility of antrum but not on the motility of duodenum in the fasted state of animals. Obestatin exerts inhibitory effects on the motility of antrum and duodenum in the fed state but not in the fasted state of animals. NPY Y2 and Y4 receptors in the brain may mediate the action of ghrelin, CRF type 2 receptor in the brain may mediate the action of des-acyl ghrelin, whereas CRF type 1 and type 2 receptors in the brain may mediate the action of obestatin.     

Somatostatin and the interdigestive migrating motor complex in man

The relationship between somatostatin and the interdigestive migrating motility complex (MMC) was determined in human volunteers. Motor activity was monitored manometrically by means of seven perfused catheters: four in the stomach, one in the duodenum, two in the jejunum. Blood samples were drawn every 10 min and radioimmunoassayed for motilin, pancreatic polypeptide and somatostatin. In four volunteers two activity fronts (AF) were recorded and somatostatin levels correlated to the manometric data. The start of an AF in the upper duodenum was accompanied by somatostatin peaks. Peak values, taken as the mean of the levels in the sample obtained after the start of an AF, the preceding sample and the next one, averaged 32 +/- 4 pM compared to 12 +/- 2 pM in the remaining period. In four volunteers somatostatin was infused in doses of 1.2, 2.4 and 4.8 pM/kg per min over three consecutive periods of 90 min, causing dose-dependent increments in plasma somatostatin levels of 7, 32 and 76 pM. In all volunteers and for all doses all gastric activity was completely inhibited. In the intestine phase 2 was abolished but phase 3 stimulated: during somatostatin infusion phase 3 occurred with an interval of 39 +/- 6 min. Motilin and PP levels were decreased. As the two lowest infusion doses caused increases in somatostatin levels that might be considered as physiological, somatostatin seems to have a physiological role in the regulation of the migrating motor complex. We propose that it facilitates the progressing of the activity front into the small intestine.     

Characteristic features in the "laryngotrachea" of Suncus murinus

In the larynx of the Suncus murinus (house musk shrew), the cricoid cartilage was situated laterally to and overlapped with the 1st, the 2nd, and a part of the 3rd tracheal cartilages. The term "laryngotrachea" was used for the region maintained by both the cricoid cartilage and the tracheal ones. It is suggested that the condition of the cartilages in Suncus laryngotrachea is the most primitive condition in mammals. In the dorsal wall, just caudal to the plate of the cricoid cartilage and dorsal to the 3rd tracheal cartilage, there existed the "L-shaped cartilage" (named by the authors).     

Molecular identification of GHS-R and GPR38 in Suncus murinus

We previously identified ghrelin and motilin genes in Suncus murinus (suncus), and also revealed that motilin induces phase III-like strong contractions in the suncus stomach in vivo, as observed in humans and dogs. Moreover, repeated migrating motor complexes were found in the gastrointestinal tract of suncus at regular 120-min intervals. We therefore proposed suncus as a small laboratory animal model for the study of gastrointestinal motility. In the present study, we identified growth hormone secretagogue receptor (GHS-R) and motilin receptor (GPR38) genes in the suncus. We also examined their tissue distribution throughout the body. The amino acids of suncus GHS-R and GPR38 showed high homology with those of other mammals and shared 42% amino acid identity. RT-PCR showed that both the receptors were expressed in the hypothalamus, medulla oblongata, pituitary gland and the nodose ganglion in the central nervous system. In addition, GHS-R mRNA expressions were detected throughout the stomach and intestine, whereas GPR38 was expressed in the gastric muscle layer, lower intestine, lungs, heart, and pituitary gland. These results suggest that ghrelin and motilin affect gut motility and energy metabolism via specific receptors expressed in the gastrointestinal tract and/or in the central nervous system of suncus.     

Existence of an endothelio-endothelial placenta in the insectivore,Suncus murinus

Summary The interhemal membrane of the chorioallantoic placenta in the insectivore Suncus murinus was investigated by means of electron microscopy. In the interhemal membrane the syncytiotrophoblast clearly intervened between the hypertrophied maternal endothelium and the fetal endothelium by day 20 of pregnancy. Although the syncytiotrophoblast showed a sieve-like feature from day 20 to 24, it was distinctly continuous. The syncytiotrophoblast, however, became discontinuous in most areas of the labyrinthine zone after day 24, and finally both projections of the maternal and the fetal endothelium contacted each other. These findings indicate the focal existence of an endothelio-endothelial condition within an otherwise endothelio-chorial placenta.     

An immunohistochemical study on the distribution of endocrine cells in the gastrointestinal tract of the musk shrew, Suncus murinus

The endocrine cells in the gastrointestinal tract of the musk shrew were studied immunohistochemically. Eleven kinds of endocrine cells, immunoreactive for serotonin, somatostatin, gastrin, cholecistokinin, gastric inhibitory polypeptide, motilin, secretin, neurotensin, pancreatic glucagon, enteroglucagon and bovine pancreatic polypeptide, were revealed. In the stomach, serotonin-, somatostatin-, gastrin-, pancreatic glucagon- and enteroglucagon-immunoreactive cells were detected. The first three types of cells predominated and were more abundant in the pyloric glands than in the other stomach regions. In the small intestine, all types of endocrine cells were found, each having different distributions and relative frequencies. In the large intestine, 10 types of endocrine cells except cholecystokinin-immunoreactive cells were detected. Serotonin- and bovine pancreatic polypeptide-immunoreactive cells were more numerous in the large intestine than in the small intestine.     

Unusual features of sperm ultrastructure in the musk shrew Suncus murinus

The spermatozoon of the Musk shrew Suncus murinus displays unusual fine anatomical features. In the head, the equatorial segment of the acrosome is recessed within a waist in the sperm nucleus in a way that could afford some protection for this fusogenic region, perhaps during penetration of the egg vestments. The perinuclear material has distinctive inner and outer regions, the latter being arranged as a series of coxcomblike spikes. These structures in Suncus could serve to anchor its characteristically giant acrosome to the sperm nucleus. In the tail, small aggregations of electron dense material appear against some centriolar triplets and also, proximally, against some axonemal doublets. In the midpiece, prominent satellite material aggregates proximally over the inner border of the dense fibers. More distally, the material maintains a close relationship with and primarily lies between the corresponding axonemal doublets and dense fibers 5 and 6, the latter being positioned asymmetrically in relation to the remaining dense fibers.     

Estrogen binding component in the pilosebaceous tumor developed in Suncus murinus

We transplanted a pilosebaceous tumor developed on the sidegland of Suncus murinus to male nude athymic (BALB/c-nu/nu) mice. This tumor can be transplanted to female hosts as well, with a lower rate of graft-taking and slower growth rate. In this study we demonstrated the presence of macromolecules which specifically bind to estrogen. Measurement of 17 beta-estradiol (E2) binding by a dextran-coated charcoal assay revealed that the number of binding sites and the dissociation constant were 22.3 +/- 4.6 fmol/mg protein and 1.4 +/- 0.24 X 10(-9) M, respectively. This binding was specific for E2 and diethylstilbestrol (DES). Sucrose gradient centrifugation of the [3H]E2-labeled cytosol yielded a sharp peak of radioactivity at 3.5S-4S under high salt conditions and a 9S peak with a shoulder at 3.5S under low salt conditions. This 3.5S shoulder was due to dissociation of [3H]E2 from the 9S peak during the centrifugation, since only the 9S peak was obtained by postlabeled density gradient analysis. An assay of the in vivo binding of [3H]E2 showed significant radioactivity in the nuclear extract from the tumor. This nuclear uptake was markedly decreased by simultaneous administration of 100-fold excess of E2. In tumor-bearing castrated nude mice, 1-100 micrograms/day of E2 did not affect tumor growth, whereas it counteracted the stimulative effect of testosterone propionate.     

Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

The development of the small intestine in the insectivore Suncus murinus was noted during the period from 21 days' gestation to 20 days after birth. At 21 days of gestation, the proximal small intestine exhibited the beginning of villus formation, whereas the distal small intestine preserved the stratified epithelium. Stratified epithelium in the distal small intestine changed into a single layer by 24 days' gestation. At 26 days' gestation, each epithelial cell was immature; but by 28 days mature-looking epithelial cells were found. The shape of the villi changed from cuboid to columnar during the same period. The connective-tissue cores of the villi began to develop at 7 days after birth in the proximal small intestine and at 15 days after birth in the distal small intestine. Crypts appeared at 15 days after birth. Endocytosis of epithelial cells took place at 28 days of gestation. In the proximal small intestine, supranuclear vesicle clusters were observed first at birth; they began to decrease both in number and size at 10 days' gestation and then disappeared completely by 20 days after birth. In the distal small intestine, large supranuclear vacuoles were observed first at 28 days of gestation. Although these vacuoles invariably were found up to 15 days after birth, they also disappeared completely by 20 days. Epithelial cells showed a structure similar to those of the adult after weaning.     

Computational model of the migrating motor complex of the small intestine

The migrating motor complex (MMC) is a cyclic motor pattern with several phases enacted over the entire length of the small intestine. This motor pattern is initiated and coordinated by the enteric nervous system and modulated by extrinsic factors. Because in vitro preparations of the MMC do not exist, it has not been possible to determine the intrinsic nerve circuits that manage this motor pattern. We have used computer simulation to explore the possibility that the controlling circuit is the network of AH/Dogiel type II (AH) neurons. The basis of the model is that recurrent connections between AH neurons cause local circuits to enter a high-firing-rate state that provides the maximal motor drive observed in phase III of the MMC. This also drives adjacent segments of the network causing slow migration. Delayed negative feedback within the circuit, provided by activity-dependent synaptic depression, forces the network to return to rest after passage of phase III. The anal direction of propagation is a result of slight anal bias observed in projections of AH neurons. The model relates properties of neurons to properties of the MMC cycle: phase III migration speed is governed by neuron excitability, MMC cycle length is governed by the rate of recovery of synaptic efficacy, and phase III duration is governed by duration of slow excitatory postsynaptic potentials in AH neurons. In addition, the model makes experimental predictions that can be tested using standard techniques.     

Planned reproduction of the house musk shrew (Suncus murinus)

To investigate methods for the planned reproduction of the house musk shrew (Suncus murinus), increased reproduction was attempted from May through August, 1980 using 13 females and 13 males obtained from the breeding colony in the Laboratory of Animal Genetics, Faculty of Agriculture, Nagoya University. As a result, a reproduction colony consisting of 128 females and 60 males was formed in September, 1981. This was followed by repeated selective culling until a planned reproduction system with monthly production of over 100 pups was established in December, 1981. The production results for one year, 1982, showed that among the 994 females mated, there was a gestation rate of 74.1%, a parturition rate of 89.8%, average litter size of 3.5, a weaning rate of 77.2%, and a productive index of 1.8. A total of 1,780 weanlings was obtained and stable production throughout the year was achieved.     

Serum constituents and liver photomicrographs of wild Suncus murinus in the south of Taiwan

Serum constituents and liver of the wild male suncus as well as of those bred and fed in our laboratory were examined serologically and histologically. The following results were obtained: The serum glutamic-oxaloacetic transaminase, gamma-glutamyl transaminase, inorganic phosphate, blood urea nitrogen, creatinine, uric acid, and zinc turbidity test levels of wild suncus were higher than those of 4 and 8 week old fed suncus. The total cholesterol level of wild suncus was lower than those of 4 and 8 week old fed suncus. In wild suncus, the total bilirubin and direct bilirubin levels were higher, and the Ca and albumin levels were lower than those of 4 week old fed suncus. However, no significant differences were observed between the wild and the 8 week old fed suncus. Although the alkaline phosphatese and thymol turbidity test levels of wild suncus were larger than those of 8 week old fed suncus, no significant differences were observed between the wild and the 4 week old fed suncus. The histological study revealed the presence of fatty droplets in only 2 of the 67 wild suncus examined while fatty droplets (grade +) were observed in almost all the fed suncus. In one case of the wild suncus, moderate round cell infiltration in interlobular connective tissue was found.