Musk Shrew Suncus Murinus Research Articles

Selective inhibition of small-diameter axons using infrared light

Novel clinical treatments to target peripheral nerves are being developed which primarily use electrical current. Recently, infrared (IR) light was shown to inhibit peripheral nerves with high spatial and temporal specificity. Here, for the first time, we demonstrate that IR can selectively and reversibly inhibit small-diameter axons at lower radiant exposures than large-diameter axons. We provide a mathematical rationale, and then demonstrate it experimentally in individual axons of identified neurons in the marine mollusk Aplysia californica, and in axons within the vagus nerve of a mammal, the musk shrew Suncus murinus. The ability to selectively, rapidly, and reversibly control small-diameter sensory fibers may have many applications, both for the analysis of physiology, and for treating diseases of the peripheral nervous system, such as chronic nausea, vomiting, pain, and hypertension. Moreover, the mathematical analysis of how IR affects the nerve could apply to other techniques for controlling peripheral nerve signaling.

Incidence of dental lesions in musk shrews (Suncus murinus) and their association with sex, age, body weight and diet

Both wild and laboratory strains of the musk shrew (Suncus murinus) have a high incidence of periodontitis. The authors completed necropsy examinations in 51 shrews to identify dental lesions including tooth loss, mobility and fractures. Dental lesions were identified in significantly more females than males, and older animals were more likely to have lesions present. Shrews with one or more dental lesions weighed significantly less than those without lesions present. Dietary supplementation with mealworms did not significantly affect the incidence of dental lesions or the body weight of male or female shrews. The authors recommend routine body weight measurement as a simple, noninvasive method of detecting shrews with an increased likelihood of having dental lesions.

Effect of daily linear acceleration training on the hypergravity-induced vomiting response in house musk shrew (Suncus murinus)

The effects of repeated linear acceleration training and the antimotion sickness drug, promethazine, on hypergravity-induced motion sickness were examined in musk shrew (Suncus murinus), which is known to show a vomiting response to motion stimulation. Animals were assigned into five groups: vestibular intact, untreated animals (Sham), vestibular lesioned (VL) animals, vestibular intact animals with promethazine hydrochloride administered as daily drinking water (Prom), vestibular intact animals who underwent horizontal linear accelerator motion training (Train), and vestibular intact animals treated with both promethazine hydrochloride and linear acceleration training (Prom+Train). In Sham animals, the number of vomiting episodes was 14±2 during 2 G exposure for 10min, and was accompanied by intense Fos expression in the medial vestibular nucleus (MVe), the nucleus of the solitary tract (NTS), the area postrema (AP), and the paraventricular hypothalamic nucleus (PVN). The vomiting response and Fos expression were completely abolished in VL animals, indicating that these responses are mediated via the vestibular system. Although Train and Prom animals experienced a significantly reduced number of hypergravity-induced vomiting episodes compared with Sham animals, the effect was significantly greater in Train animals than in Prom animals. Fos expression in the NTS, AP, and PVN were significantly more reduced in Train animals than in Prom animals. Higher dose of bolus injection of promethazine (50mg/kg, i.p.) completely abolished the vomiting episodes, although the animals were drowsy and sedated due to side effects. In conclusion, daily linear acceleration training and promethazine could prevent the hypergravity-induced vomiting episodes.

Intermittent Esophageal Hypotensive Peristalsis Re-Assessed With Multiple Rapid Swallowing

We recently proposed the usefulness of the house musk shrew (Suncus murinus ) as a model animal for motilin study because this animal produces a motilin family peptide and shows the phasic interdigestive gastric contraction. This gastric motor contraction includes phase I, phase II and phase III contractions as found in dogs and humans. In the DDW 2010, we reported that cumulative ghrelin administration and pretreatment with a low dose of motilin (10−10 M) synergistically induced gastric contraction in a dose-dependent manner, suggesting that ghrelin is involved in the migrating motor complex (MMC) and has a complementary effect with motilin. To clarify the effects of these family peptides on each phase in the MMC, we administrated an antagonist of motilin or ghrelin into a force transducer-sutured freemoving suncus. At 10-20 min after the beginning of phase II contraction, MA-2029 (1 mg kg−1 h−1, motilin receptor antagonist) or saline was continuously infused for 2 h, and we found that phase II-like contraction was prolonged and that no phase III contraction occurred during the infusion of MA-2029. The duration from the start of infusion of the motilin antagonist and phase III contraction was significantly longer (182 ± 12 min) than that in controls (71 ± 6 min, P<0.05). These results indicate that motilin has no effect on continuing phase II contraction but is essential for induction of phase III contraction. The frequencies of phasic contraction with saline treatment and MA-2029 treatment were almost the same in phase II (saline: 14 ± 0.7 min−1, MA-2029: 13 ± 0.7 min−1). Although bolus administration of motilin (300 ng kg−1 i.v.) significantly induced phase III-like contraction in the control suncus In Vivo, during the infusion of MA-2029, motilin administration (300 ng kg−1) did not evoke phase III-like contraction. On the other hand, continuous infusion of D-Lys3GRHP6 (6 mg kg−1 h−1, ghrelin receptor antagonist) for 2 h inhibited phase II contraction and completely suppressed phase III contraction, and phase II contraction restarted after the end of infusion. The results of this study together with the results of our previous study showing that ghrelin administration (0.1, 0.2 μg kg−1 min−1 for 10 min i.v.) in phase II of MMC significantly enhanced gastric contraction in a dose-dependent manner indicated that MMC in the free-moving suncus stomach is coordinated by endogenous motilin and ghrelin. Phase II contraction may be initiated by endogenous ghrelin, and subsequent increase in motilin induces following phase III contraction.

Effect of TZP-201, a novel motilin receptor antagonist, in the colon of the musk shrew (&lt;I&gt;Suncus murinus&lt;/I&gt;)

Motilin is the main gut peptide that stimulates propulsive motility in the upper gastrointestinal (GI) tract. Motilin receptors exist in the colon but little is known about their functional role, and species-dependent differences present a major obstacle to understanding the physiological significance and potential therapeutic implications of motilin receptors in the colon. Our study aimed to define whether a motilin receptor is functionally expressed in the colon of the Asian musk (or house) shrew (Suncus murinus) and to investigate the effect of a novel motilin receptor antagonist, TZP-201. GI tissue (gastric antrum, small intestine and colon) was isolated from male shrews and the effects of a motilin receptor agonist [Nle13]motilin and the antagonist TZP-201 on contractile activity and mucosal electrogenic transport of water and electrolytes were investigated in vitro. [Nle13]motilin induced a moderate increase in spontaneous contractility in the stomach and no significant changes in the small intestine; a marked increase in contractility was found in the colon. Motilin-induced contractions in the colon were abolished by tetrodotoxin or atropine, and dose-dependently inhibited by 0.01-10 muM TZP-201. Neither [Nle13]motilin nor TZP-201 had any effect on basal mucosal transport. Shrew colon expresses a functional motilin receptor that induces contractile activity by the activation of enteric cholinergic neurons. TZP-201 inhibited motilin-induced colonic contractions. Motilin antagonists may represent a new approach for the treatment of GI motility disorders characterised by hypercontractility.

Oculocutaneous Albinism in Suncus murinus: Establishment of a Strain and Identification of Its Responsible Gene

The house musk shrew Suncus murinus (Insectivora, Soricidae) is referred to as suncus in a laboratory context. Although the capture of albino-like shrews (wild suncus) has been reported previously, albino-like strains have never been established, and the molecular basis of the character has remained elusive. We have established an OCAO mutant strain (oculocutaneous albinism Okinawa), from a wild suncus with a white coat and red eyes, which was captured in 2002. During the course of establishing the strain, it was revealed that the albino-like phenotype was inherited in an autosomal recessive manner. To elucidate the molecular basis of this phenotype, we cloned the suncus cDNAs for tyrosinase (Tyr), pink-eyed dilution (p), and solute carrier family 45, member 2 (Slc45a2), since these genes are involved in oculocutaneous albinism in various species, including humans. Several polymorphisms were identified in these genes; however, linkage analysis excluded the involvement of Tyr and p. On the other hand, two amino acid substitutions (V240A and G366E) were identified in Slc45a2 that cosegregated with the phenotype in the OCAO mutant strain. While V240A was also present in colored suncus collected from Okinawa, G366E was unique to the albino-like suncus and heterozygous carriers. Thus, we conclude that a mutation in Slc45a2 (G366E) is responsible for an albino-like phenotype in Suncus murinus.

Changes in Localization of Steroidogenic Enzymes and Steroid Hormone Receptors in the Musk Shrew (Suncus murinus).

Changes in Localization of Steroidogenic Enzymes and Steroid Hormone Receptors in the Musk Shrew (Suncus murinus).

Numerical variation of teeth in the wild house musk shrew Suncus murinus captured from Nagasaki, Japan

Wild populations of Suncus murinus from Nagasaki were thought to be extinct, although specimens from Nagasaki are kept at the National Science Museum, Tokyo. Variation in the number of teeth, including both congenital and postnatal absence, was observed in 25 of 85 individuals. All 25 abnormal individuals were checked using a micro-CT unit to document the presence or absence of embedded teeth and any traits of postnatal absence. Four of these had congenitally absent teeth, whereas the rest showed signs of postnatal absence. There was no significant difference in the ratio of length of tooth group P 4M 3 against palatal length between individuals with congenital absent teeth and normal ones. Because S. murinus in captivity shows a high rate of periodontal disease, we suggest that the high rate of postnatal absence of teeth in the wild population is due to oral diseases such as periodontal disease or other traumatic factors.

The untamed shrew: on the termination of an eradication programme for an introduced species

Summary One option in managing introductions of non‐native pest species is to eradicate the introduced species by trapping or otherwise removing individuals. A central issue in undertaking such a programme is deciding when it is reasonable to terminate the programme because all individuals have been removed. This decision requires knowledge of the probability that complete eradication has been achieved. An objective Bayesian method is presented to determine the probability that all individuals of an introduced species have been removed. The method is based on the excess trapping times of individuals beyond a specified threshold, assuming a generalized Pareto distribution for excess trapping time. The method is applied to data from an unsuccessful trapping programme of the Asian musk shrew Suncus murinus on the Mauritian island of Ile aux Aigrettes. The results suggest that, had the method been used, managers would have realized that the probability of complete eradication was not high and premature termination could have been avoided. Synthesis and applications. A central issue facing the manager of an eradication programme for an introduced or pest species is deciding when it is reasonable to terminate the programme because all individuals have been removed. If termination is premature, the programme will fail; if termination is delayed beyond the point of eradication, unnecessary costs will be incurred. The statistical method described here for calculating the probability of complete eradication based on the record of removals provides information that is useful either in an informal assessment of progress or in more formal decision making regarding termination.

Phylogeography of Wild Musk Shrew (Suncus Murinus) Populations in Asia Based on Blood Protein/Enzyme Variation

The musk shrew (Suncus murinus) is an insectivore species that inhabits tropical and subtropical Asia widely. To clarify the genetic relationship among wild musk shrew populations, we examined the electrophoretic variants of biparentally inherited genetic markers at 10 loci coding for eight blood proteins/enzymes in a total of 639 animals and compared the results obtained from the mitochondrial DNA data. The principal-component analysis performed using the allele frequency data revealed that the 17 populations could be divided into two major groups, a South Asian group and a Southeast Asian group that includes several island populations bound by Myanmar. The degrees of genetic divergence among populations were higher within the Southeast Asian group than within the South Asian group. This finding was incongruent with the mtDNA diversity. Analysis conducted at the individual level showed that a shrew from the central region in Myanmar that carries a South Asian type of mtDNA showed the electrophoretic variants specific to the Southeast Asian group, suggesting that this region is a contact zone between the two major groups.

Topographical Representation of Motoneurons Innervating the Transverse Mandibular Muscle in the Trigeminal Motor Nucleus, with Special Reference to Rats

Localization of motoneurons of the transverse mandibular muscle (TM) was examined by a retrograde tracing method (horseradish peroxidase (HRP) and wheat germ agglutinin-HRP (WGA-HRP) ) in the rat (rodent), house musk shrew (Suncus murinus, insectivore) and miniature pig (even-toed, ungulate). In the injection of HRP solution into the TM of the rat, labeled neurons with HRP appeared at the lateral and ventral margins of the dorsolateral division in the rostral two-thirds level of the trigeminal motor nucleus. This distribution area was close to or overlapped that of medial pterygoid and lateral pterygoid motoneurons. TM motoneurons of the shrew and pig were located in the ventromedial part of the dorsolateral division at the rostral half level of the nucleus. The distribution patterns of each masticatory muscle motoneuron in the rat were also confirmed for comparison with those of TM motoneurons. Electromyography during feeding in the rat showed that TM activity almost synchronized with the activities of both jaw-closer and jaw-opener muscles.

Cloning of Putative Uncoupling Protein 1 cDNA in a Cold-intolerant Mammal, the House Musk Shrew (Suncus murinus)

The house musk shrew (Suncus murinus), or suncus, is a unique experimental animal. We recently showed that this mammal is cold intolerant and hypothesized that its sensitivity to cold is caused by low thermogenic activity in brown adipose tissue (BAT). Thermogenesis in BAT is performed by a unique mitochondrial protein, uncoupling protein 1 (UCP1). Interestingly, only eutherians possess UCP1, and some traits in the suncus resemble those in the Ucp1-ablated mouse, including cold intolerance, histology of BAT, and obesity resistance. In a previous study, we hypothesized that UCP1 may not be present in BAT of the suncus or may be dysfunctional. Therefore, we performed cDNA cloning of suncus Ucp1 and compared it to homologs from other species. The deduced amino acid sequence showed high similarity to other mammalian UCP1. Northern blot analysis revealed mRNA in BAT, as in other mammals. However, a difference in an amino acid residue was observed in an important residue for thermogenesis. Genomic sequence analysis showed that this difference existed in our two genetically distant laboratory colonies. These results suggest that cold intolerance in the suncus is derived from low thermogenic activity of UCP1 and may exist in wild house musk shrews.

Mechanisms underlying the failure of an attempt to eradicate the invasive Asian musk shrew Suncus murinus from an island nature reserve

The Asian musk shrew Suncus murinus is an invasive predator that has had a considerable impact on biodiversity. An eradication was attempted from Ile aux Aigrettes, a 25-ha island reserve off the coast of Mauritius as part of a wider restoration program. A total of 759 shrews were removed using up to 1112 live-traps, in six trapping sweeps of the island. After the first four sweeps, in which 705 shrews were caught, complete eradication appeared to have been achieved, with only four shrews caught in the next three months. However, thereafter shrew captures increased and after six months shrews were again being captured in large numbers. We examine three hypotheses for the failure of the eradication program: (i) low efficiency of all traps (‘low efficiency’ hypothesis); (ii) low trap efficiency in certain locations (‘refuge’ hypothesis); and (iii) presence of trap-shy individuals (‘trap-shy’ hypothesis). We constructed an individual-based simulation of the first four trapping sweeps to predict expected patterns of shrew capture for different shrew densities and capture probabilities and in the presence of trapping ‘refugia’. The observed patterns of capture were not consistent with the expected patterns of capture under the ‘low efficiency’ and ‘refuge’ hypotheses, but were intuitively consistent with the ‘trap-shy’ hypothesis. We use the results from this study to help plan future eradication programs for S. murinus.

Type 1 iodothyronine deiodinase in the house musk shrew ( Suncus murinus, Insectivora: Soricidae): cloning and characterization of complementary DNA, unique tissue distribution and regulation by T 3

The house musk shrew Suncus murinus (Insectivora: Soricidae) has been reported as having low thyroxine to 3,3 ′5-triiodothyronine (T 3) converting activity in liver and kidney homogenates and was assumed to be type 1 iodothyronine deiodinase (D1)-deficient. To study whether this is due to structural abnormality of shrew D1, we cloned the cDNA and characterized the enzyme. The deduced amino acid sequence of shrew D1 was found to be highly homologous to other known D1s and the enzyme itself to have similar catalytic activity. However, unlike in other species, the D1 activity was detected only in liver. Moreover, the D1 activity in liver of the shrew was less than half of that in rat liver and its expression was not up-regulated by T 3. In contrast, a very high activity of D2 was demonstrated in brain and brown adipose tissue. The present study also revealed that the serum level of T 3 in the shrew was in the same range as these in other mammals. These results suggest that D2 contributes to the production and maintenance of T 3 levels in the house musk shrew.

Three-dimensional distribution patterns of PRL, GH and ACTH cells in the house musk shrew ( Suncus murinus).

Despite a multitude of reports on the classification and distribution of anterior pituitary cells, no previous study has attempted to obtain the three-dimensional (3D) and computer-graphic distribution pattern of each cell type in the whole pituitary. Therefore, we mapped the anterior pituitary cells of the house musk shrew ( Suncus murinus) and found a distinct cellular distribution pattern. Serial horizontal sections of whole shrew pituitaries were stained immunohistochemically for prolactin (PRL), growth hormone (GH), and adrenocorticotropic hormone (ACTH) cells. The contours of positive cells and the anterior, intermediate, and posterior lobes in each section were digitized for 3D visualization by a volume rendering method. The reconstructed images and virtual frontal and sagittal slices were examined in detail. On the 3D reconstructed images, the PRL and GH cells had similar distribution patterns, although the former were concentrated in the dorsolateral and ventrocentral portions, and the latter in the dorsocentral portions of the anterior lobe. On both sides of the pituitary stalk, there lay portions that were conspicuous by scarcity of PRL and GH cells. ACTH cells were widely scattered throughout the whole anterior lobe, but they were very few in the above portions and the dorsocentral portions where GH cells were concentrated. No sex difference in the distribution patterns of each cell type was observed. However, PRL cells in females were more numerous than in males, whereas the opposite was true for GH and ACTH cells. We discuss the relationship between the formation of the spatial distribution patterns and anterior pituitary ontogeny.

Amphetamine and morphine produce a conditioned taste and place preference in the house musk shrew (Suncus murinus).

Rats have been shown to avoid consuming a flavor, but prefer a location, previously paired with amphetamine or morphine. A series of 4 experiments evaluated the hedonic properties of amphetamine and morphine in the house musk shrew (Suncus murinus), an insectivore that (unlike rats) is capable of vomiting when exposed to toxins. Unlike rats, amphetamine (20 mg/kg) and morphine (20 mg/kg) produced both a conditioned sucrose (0.3 M) and saccharin (0.1%) preference in shrews (administered intraperitoneally), when measured by both a 1- and a 2-bottle test. At the same dose, both drugs also produced a place preference in shrews. These results suggest that the potential of rewarding drugs to produce taste avoidance may vary on the basis of the ability of the species to vomit.

Vasopressin Induces Emesis in Suncus murinus

This paper reports that vasopressin is emetogenic in the house musk shrew Suncus murinus. Either intravenous or intracerebroventricular administration of vasopressin caused vomiting within a few minutes. The ED50 of intravenous vasopressin was as high as 4.67 μ g /kg, whereas intracerebroventricularly injected vasopressin was effective at a low dose of 20 ng /brain. The emetogenic target of vasopressin may therefore be present in the central nervous system. We propose the Suncus as a useful animal for investigation of vasopressin-mediated emesis, including motion sickness.

Chromosomal Mapping of 18S-28S rRNA Genes and 10 cDNA Clones of Human Chromosome 1 in the Musk Shrew (Suncus murinus)

The direct R-banding fluorescence in situ hybridization (FISH) method was used to map 18S-28S ribosomal RNA genes and 10 human cDNA clones on the chromosomes of the musk shrew (Suncus murinus). The chromosomal locations of 18S-28S ribosomal RNA genes were examined in the five laboratory lines and wild animals captured in the Philippines and Vietnam, and the genes were found on chromosomes 5, 6, 9, and 13 with geographic variation. The comparative mapping of 10 cDNA clones of human chromosome 1 demonstrated that human chromosome 1 consisted of at least three segments homologous to Suncus chromosomes (chromosomes 7, 10, and 14). This approach with the direct R-banding FISH method is useful for constructing comparative maps between human and insectivore species and for explicating the process of chromosomal rearrangements during the evolution of mammals.

Comparison of sucrase-free isomaltase with sucrase-isomaltase purified from the house musk shrew Suncus murinus

We purified sucrase-isomaltase and sucrase-free isomaltase from a normal and a sucrase-deficient line, respectively, of the house musk shrew Suncus murinus and examined the effects of mutation on enzyme structure and activities. Recent cDNA cloning studies have predicted that sucrase-free mutant isomaltase lacks the C-terminal 69 amino acids of normal isomaltase, as well as the entire sucrase. On SDS-polyacrylamide gel electrophoresis purified sucrase-free isomaltase gave a single protein band of 103 kDa, while sucrase-isomaltase gave two major protein bands of 106 and 115 kDa. The 115, but not 106, kDa band was quite similar to the 103 kDa band on Western blotting with Aleuria aurantia lectin and antibody against shrew sucrase-isomaltase, suggesting that the 115 and 103 kDa bands are due to normal and mutant isomaltases, respectively, in accordance with the above prediction. Purified isomaltase and sucrase-isomaltase were similar in K m and V max (based on isomaltase mass) values for isomaltose hydrolysis and in inhibition of isomaltase activity by antibody against rabbit sucrase-isomaltase, suggesting that the enzymatic properties of isomaltase are mostly unaffected by mutation.

Chromosomal and genic mechanisms of reproductive isolation: the case of Suncus murinus

In this paper we review the results of our studies on the relative contribution of chromosomal and genic divergence in the formation of reproductive isolation in the house musk shrew Suncus murinus (Linnaeus, 1766).