Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Shrews”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2001

Tripartite genetic subdivisions in the ornate shrew (Sorex ornatus).

We examined cytochrome b sequence variation in 251 ornate shrews (Sorex ornatus) from 20 localities distributed throughout their geographical range. Additionally, vagrant (S. vagrans) and montane (S. monticolus) shrews from four localities were used as outgroups. We found 24 haplotypes in ornate shrews from California (USA) and Baja California (Mexico) that differed by 1-31 substitutions in 392 bp of mitochondrial DNA (mtDNA) sequence. In a subset of individuals, we sequenced 699 bp of cytochrome b to better resolve the phylogeographic relationships of populations. The ornate shrew is phylogeographically structured into three haplotype clades representing southern, central and northern localities. Analysis of allozyme variation reveals a similar pattern of variation. Several other small California vertebrates have a similar tripartite pattern of genetic subdivision. We suggest that topographic barriers and expansion and contraction of wetland habitats in the central valley during Pleistocene glacial cycles account for these patterns of genetic variation. Remarkably, the northern ornate shrew clade is phylogenetically clustered with another species of shrew suggesting that it may be a unique lowland form of the vagrant shrew that evolved in parallel to their southern California counterparts.

Animals↗
PubMed2006

Tactile guidance of prey capture in Etruscan shrews.

Whereas visuomotor behaviors and visual object recognition have been studied in detail, we know relatively little about tactile object representations. We investigate a new model system for the tactile guidance of behavior, namely prey (cricket) capture by one of the smallest mammals, the Etruscan shrew, Suncus etruscus. Because of their high metabolic rate and nocturnal lifestyle, Etruscan shrews are forced to detect, overwhelm, and kill prey in large numbers in darkness. Crickets are exquisitely mechanosensitive, fast-moving prey, almost as big as the shrew itself. Shrews succeed in hunting by lateralized, precise, and fast attacks. Removal experiments demonstrate that both macrovibrissae and microvibrissae are required for prey capture, with the macrovibrissae being involved in attack targeting. Experiments with artificial prey replica show that tactile shape cues are both necessary and sufficient for evoking attacks. Prey representations are motion- and size-invariant. Shrews distinguish and memorize prey features. Corrective maneuvers and cricket shape manipulation experiments indicate that shrew behavior is guided by Gestalt-like prey descriptions. Thus, tactile object recognition in Etruscan shrews shares characteristics of human visual object recognition, but it proceeds faster and occurs in a 20,000-times-smaller brain.

Animals↗
PubMed1994

Patterns of sequence variation in the mitochondrial D-loop region of shrews.

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D-loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.

Animals↗
PubMed2001

Comparative FISH mapping of human cDNA clones to chromosomes of the musk shrew (Suncus murinus, Insectivora).

Forty-one cDNA clones of human functional genes were newly mapped to chromosomes of the musk shrew (Suncus murinus, Insectivora) by fluorescence in situ hybridization, and a comparative cytogenetic map of 51 genes, including 10 genes reported in our previous study, was constructed between human (HSA) and musk shrew (SMU) chromosomes. In this comparative map, the 51 genes localized to human autosomes, except HSA 8, 16, and 20, were mapped to 15 shrew autosomes, except SMU 4, 16, 17 and 18. Twelve conserved segments were identified between human and shrew chromosomes, and six segments among the musk shrew, human, and mouse. Our results defined the presence of at least one inversion and several interchromosomal rearrangements that occurred during evolution after the two species diverged from a common ancestor. Localization of three major histocompatibility complex (MHC) genes to shrew chromosome 3 suggested that the MHC genes of the musk shrew are located in a cluster on chromosome 3. The cytogenetic map constructed in this study is the first cytogenetic map with many functional genes in insectivore species. This approach provides clues for clarifying the chromosomal evolution in this order.

Animals↗
PubMed1995

Sedative effect of medetomidine and its reversal by atipamezole in house musk shrews (Suncus murinus).

This study was undertaken to evaluate the sedative effect of medetomidine, an alpha 2-adrenoceptor agonist, and the counteractive effect of atipamezole, an antagonist to medetomidine, in house musk shrews (Suncus murinus). Two hundred, 300, 400, or 600 micrograms/kg of medetomidine was intraperitoneal injected into 89 house musk shrews. A sedative effect was produced in one to two minutes after injection. The dose-dependent prolongation of the sedative duration and the dose-dependent appearance of a hypothermic effect were demonstrated. With 200 micrograms/kg of medetomidine, the sedative effect obtained was not adequate in some of the animals. With 300 micrograms/kg and above, a stable sedative state was induced in all the animals. The duration of sedation in the house musk shrews was much longer (p < 0.01) in males than in females. This suggested the higher susceptibility of male house musk shrews to this drug. The sedative effect and hypothermia obtained with 400 micrograms/kg of medetomidine were completely counteracted by more than 2.0 mg/kg of atipamezole. With 0.5 and 1.0 mg/kg of atipamezole, only a partial antagonistic action was produced. Transient vomiting appeared in 4.5% of the house musk shrews at approximately one minute after injection of medetomidine. This side-effect had occurred before the sedative effect was obtained, and was not serious enough to be a problem. None of the 89 house musk shrews died in this experiment. The above results show that the combination of medetomidine and atipamezole is a highly effective and safe anesthetic treatment which permits easy handling of house musk shrews.

Adrenergic alpha-Antagonists↗
PubMed1998

Open eyelids at birth, a new mutation in the musk shrew, Suncus murinus.

The mutation designated "open eyelids at birth" arose spontaneously in the BAN strain of the musk shrew (Suncus murinus). This is the first report on this kind of mutation in the shrew. Mating experiments suggested that the mutant character is controlled by an autosomal recessive gene with about 43% penetrance. The symbol oeb(open eyelids at birth) was proposed for the mutant gene. Affected shrews were fully viable and fertile. Phenotypically, the affected shrews were characterized by one or both eyelids open at birth. By 9 days of age, the exposed and dried eyeballs usually dropped off and became missing or sometimes looked microphthalmic. Except for the eye abnormality, the affected shrews showed no obvious external abnormalities. Light-microscopically, the affected shrews with missing eyes or microphthalmia-like eyes did not have complete eye structures, and only remnants of some eye tissue were observed. In the phenotypically normal oeb/oeb shrews with closed eyelids at birth, no histological eye abnormalities were noted. Thus, the mutant character observed may simply be caused by a failure of the eyelids to close.

Animals↗
PubMed1989

Development of a laboratory line (SRI line) derived from the wild house musk shrew, Suncus murinus, indigenous to Sri Lanka.

Five male and 9 female house musk shrews (Suncus murinus) captured in Koralawella, Sri Lanka were acquired by our laboratory. One male and 3 females alone contributed to the development of a new laboratory line (SRI line). The SRI line has been maintained as a closed breeding colony consisting of more than 40 shrews. Gestation period and litter size at birth averaged 31.2 days (43 cases) and 2.4 (43 litters), respectively. The SRI line shrews were uniformly covered with light gray fur. The body weight and total length of adult shrews averaged 72.9 g and 23.9 cm in males, and 49.6 g and 21.0 cm in females. These data indicate a body size intermediate between BAN line shrews originating from Bangladesh and Nag or OKI line shrews from Japan. The SRI shrews are also characterized by having 30 chromosomes in diploid, being the smallest number in the entire species, whereas the otherlines (Nag, OKI and BAN) all have 40 chromosomes.

Animal Husbandry↗
PubMed1990

Serum concentrations of thyroid hormones and activity of iodothyronine deiodinase in peripheral tissues of the house musk shrew, Suncus murinus.

Serum concentrations of thyroid hormones and the properties of iodothyronine deiodinase in tissues of the house musk shrew, Suncus murinus, were examined and compared with those of the rat. Serum concentrations of thyroxine (T4) and 3,3',5'-tri-iodothyronine (rT3) were higher, while the serum concentration of 3,5,3'-tri-iodothyronine (T3) was lower in the shrew than in the rat. Among liver, kidney, skeletal muscle, heart, brown adipose tissue (BAT), spleen, lung, testes and thymus homogenates of the shrew, T(4)5'-deiodinase (5'D) activity was highest in BAT, and rT3 5'D activity was highest in both the liver and BAT. Intermediate or low T3 5-deiodinase activity was noted in all tissues examined. Activity of 5'D for T4 and rT3 in liver and kidney was much lower, while that of BAT was much higher in the shrew than in the rat. Liver and kidney 5'D may be type-I and that of BAT may be type-II in the shrew, judging from its response to 6-n-propyl-2-thiouracil and iopanoic acid and substrate preference. Thus 5'D of the shrew was similar to that of the rat in type, but was different with respect to its activity in some peripheral tissues. This difference may have relevance to the low T3 state of the shrew.

Adipose Tissue, Brown↗
PubMed1980

Representation of the body surface in somatosensory area I of tree shrews, Tupaia glis.

Microelectrode mapping methods were used to determine the organization of the first somatosensory area, S-I, of tree shrews. Tree shrews were chosen for study because of their generalized body form, phylogenetic relationship to primates, and smooth, easily mapped cortex. A systematic representation of the contralateral body surface was found in an architectonically distinct zone identified as somatic koniocortex. Overall features of somatotopic organization were similar to S-I of other mammals, S-I of prosimian primates, and the Area 3b "S-I proper" representation of monkeys. Like Area 3b in monkeys and the somatic koniocortex in galagos, S-I in tree shrews is bordered caudally by cortex also responsive to somatosensory stimuli. Several aspects of S-I organization in tree shrews appear to be primitive and generalized. These include the representation of the trunk with the ventrum at the caudal margin of S-I, the restriction of the glabrous digits of the hand and foot to the rostral half of the representation and pointed rostralward, the representation of an anterior strip of the forelimb lateral to the hand, and a posterior strip of hindlimb medial to the foot representation. As in a number of other mammals, a large portion of S-I in tree shrews is devoted to the head. However, the proportion of S-I activated from the glabrous nose is greater in tree shrews than iun any previously studied mammal. We conclude that S-I of tree shrews has both specialized and generalized features, and that the generalized features importantly relate to an understanding of the evolution of the primate somatosensory system.

Animals↗
PubMed2000

Mutations in the p53 tumor suppressor gene in tree shrew hepatocellular carcinoma associated with hepatitis B virus infection and intake of aflatoxin B1.

Infection with hepadnaviruses and exposure to aflatoxin B1 (AFB1) are considered to be major risk factors in the development of hepatocellular carcinoma (HCC) in humans. A high rate of p53 mutations at codon 249 has been reported in these tumors. The tree shrew (Tupaia belangeri chinensis) is a useful animal model for the development of HCC after human hepatitis B virus (HBV) infection or AFB1 treatment. Therefore, it was of particular interest to determine whether the p53 gene in tree shrew HCCs associated with HBV infection and/or with exposure to AFB1 is affected in the same manner as in human HCCs. We determined the tree shrew p53 wild-type nucleotide sequences by RT-PCR and automatic DNA-sequencing. Tree shrew wild-type p53 sequence showed 91.7 and 93.4% homologies with human p53 nucleotide and amino acids sequences, respectively, while it showed 77.2 and 73.7% homologies in mice. One HCC and normal liver tissue from AFB1 treated and one HCC from AFB1- and HBV-treated tree shrew showed no change in p53 sequences, while three HCCs from AFB1- and HBV-treated tree shrews showed point mutations in p53 sequences. One HCC showed point mutations at codon 275, which is on the DNA-binding domain of p53 gene, which might be a cause of gain-of-function during the development of HCC. As a result, our finding indicates that tree shrews exposed to AFB1 and/or HBV had neither codon 249 mutations nor significant levels of other mutations in the p53 gene, as is the case with humans.

Aflatoxin B1↗
PubMed2003

Identification of aflatoxin M1-N7-guanine in liver and urine of tree shrews and rats following administration of aflatoxin B1.

Epidemiological studies have shown that exposure to aflatoxin B(1) (AFB(1)) and concurrent infection with hepatitis B lead to a multiplicative risk of developing liver cancer. This chemical-viral interaction can be recapitulated in the tree shrew (Tupia belangeri chinensis). As an initial characterization of this model, the metabolism of AFB(1) in tree shrews has been examined and compared to a sensitive bioassay species, the rat. Utilizing LC/MS/MS, an unreported product, aflatoxin M(1)-N(7)-guanine (AFM(1)-N(7)-guanine), was detected in urine and hepatic DNA samples 24 h after administration of 400 microg/kg AFB(1). In hepatic DNA isolated from tree shrews, AFM(1)-N(7)-guanine was the predominant adduct, 0.74 +/- 0.14 pmol/mg DNA, as compared to 0.37 +/- 0.07 pmol/mg DNA of AFB(1)-N(7)-guanine. Conversely, in rat liver, 6.56 +/- 2.41 pmol/mg DNA of AFB(1)-N(7)-guanine and 0.42 +/- 0.13 pmol/mg DNA of AFM(1)-N(7)-guanine were detected. Rats excreted 1.00 +/- 0.21 pmol AFB(1)-N(7)-guanine/mg creatinine and 0.29 +/- 0.10 pmol AFM(1)-N(7)-guanine/mg creatinine as compared to 0.60 +/- 0.12 pmol AFB(1)-N(7)-guanine/mg creatinine and 0.69 +/- 0.16 pmol AFM(1)-N(7)-guanine/mg creatinine excreted by the tree shrew. Furthermore, tree shrew urine contained 40 times more of the hydroxylated metabolite, AFM(1), than was excreted by rats. In vitro experiments confirmed this difference in oxidative metabolism. Hepatic microsomes isolated from tree shrews failed to produce aflatoxin Q(1) or aflatoxin P(1) but formed a significantly greater amount of AFM(1) than rat microsomes. Bioassays indicated that the tree shrew was considerably more resistant than the rat to AFB(1) hepatocarcinogenesis, which may reflect the significant differences in metabolic profiles of the two species.

Administration, Oral↗
PubMed2004

Alteration of p53 and p21 during hepatocarcinogenesis in tree shrews.

AIM: To investigate p53 mutation and p21 expression in hepatocarcinogenesis induced by hepatitis B virus (HBV) and aflatoxin B(1) (AFB(1)) in tree shrews, and to reveal the role of these genes in hepatocarcinogenesis. METHODS: Tree shrews were divided into four groups: group A, those infected with HBV and fed with AFB(1) (n = 39); group B, those infected with HBV alone (n = 28); group C, those fed with AFB(1) alone (n = 29); and group D, normal controls (n = 20). The tree shrews underwent liver biopsies once every 15 wk. Expression of p53 and p21 proteins and genes in the biopsies and tumor tissues of the experimental tree shrews was detected, respectively, by immunohistochemistry, and by Southern blotting and reverse transcription-polymerase chain reaction and sequencing. RESULTS: The incidence of hepatocellular carcinomas (HCC) was higher in group A (66.7%) than that in group B (3.57%) and C (30%). The time of HCC occurrence was also earlier in group A than that in group C (120.0+/-16.6 wk vs 153.3+/-5.8 wk, respectively, P<0.01). p53 protein was not detected by immunohistochemistry in all groups before the 75(th) wk of the experiment. At the 105(th) wk, the positive rates fo p53 were 78.6%, 60% and 71.4% in groups A, B and C, respectively, which were significantly higher than that in group D (10%) (all P<0.05). An abnormal band of p53 gene was observed in groups A and C. The mutation points of p53 gene in tree shrews with HCC were at codons 275, 78 and 13. The nucleotide sequence and amino acid sequence of tree shrew's wild-type p53 showed 91.7% and 93.4% homologies with those of human p53, respectively. The immunopositivity for p21 was found before HCC development. The incidence of HCC was significantly higher in tree shrews that were positive for p21 than those negative for p21 (80.0% vs 11.0%, P<0.001). The incidence of HCC in p21 positive animals in group A was significantly higher than those positive for p21 in group C (P<0.05). CONCLUSION: A remarkable synergistic effect on HCC development exists between HBV and AFB(1). p53 mutation promotes the development of HCC. HBV and AFB(1) may synergistically induce p53 gene mutation, and stimulate ras gene expression. ras gene is activated at the earlier stage during hepatocarcinogenesis. p21 protein may be an early marker, and the alterations of p53 may be a late event in the development of HCC.

Animals↗
PubMed2003

Cloning and characterization of cholesteryl ester transfer transfer protein isolated from the tree shrew.

OBJECTIVE: To obtain the nucleotide sequence and deduced amino acid sequence of cholesteryl ester transfer protein (CETP) cDNA from the tree shrew (Tupaia glis). METHODS: The cDNA sequence of the tree shrew CETP was obtained by utilizing the technique of switching mechanism at 5' end of RNA transcript (SMART) and rapid amplification of cDNA end (RACE) from the first strand of the cDNA. The amino acid sequence of CETP was deduced from the cDNA sequence and its primary and secondary structures were predicted. RESULTS: The sequence of CETP cDNA from tree shrew (GenBank accession number AF334033) covers 1636 bp, including 178 bp at the 3' end of the untranslated region and a 1458 bp fragment in a coding region, which provides the complete sequence of mature tree shrew CETP, although not the initiator methionine. The first 24 bp encodes a partial signal peptide. The mature protein consists of 477 amino acids and is longer than the human version by one amino acid (Gly318). Comparing this amino acid sequence with those of other animals' CETPs, the identity between tree shrew and human and rabbit CETP is 88% and 82%, respectively. The protein is extremely hydrophobic as it contains many hydrophobic residues, especially at the C-terminal, consistent with its function in the transfer of neutral lipids. The amino acid residues concerning with binding and transferring neutral lipids are highly conserved. There is a deletion of an N-linked glycosylation site at Asn342 in the tree shrew CETP protein that may participate in the removal of peripheral cholesterol and cholesteryl ester by increasing its activity of transferring cholesteryl ester. CONCLUSION: The possible glycosylation in the tree shrew CETP may be involved in the molecular mechanism of its insusceptibility to atherosclerosis.

Amino Acid Sequence↗
PubMed2002

[Analysis of lecithin-cholesterol acyltransferase cDNA and protein sequence from tree shrew].

OBJECTIVE: To acquire cDNA sequence of lecithin-cholesterol acyltransferase (LCAT) from tree shrew and analyze the sequence structure. METHODS: The first strand cDNA was acquired by reverse transcription using mRNA from tree shrew liver as template. By the method of SMART RACE PCR, tree shrew LCAT cDNA was acquired and deduced its amino acids sequence. The sequence and structure of tree shrew LCAT cDNA and amino acid were analyzed and predicted by the molecular software. RESULTS: Tree shrew LCAT cDNA is composed of 1,340 bp, including 2 bp 5' untranslated region (5' UTR), 1,320 bp open reading frame (ORF) which encodes protein precursor of 440 amino acids (24 amino acids signal peptide and 416 amino acids mature peptide), and 18 bp 3' untranslated region (3'UTR). The stop codon is TAA and there is a poly (A) signal sequence AATAAA and a 25 bp poly (A) tail. Tree shrew LCAT cDNA sequence has been accepted by GenBank as a new gene, accession number AF272861 and its homology with human and baboon was 90% and 89%, respectively. CONCLUSION: The sequence of LCAT cDNA in tree shrew has high identity with that of human and other experimental animal species.

Amino Acid Sequence↗
PubMed2005

[A cDNA microarray study of the differential expression of genes in signal transduction pathway during hepatocarcinogenesis in tree shrews].

OBJECTIVES: To study the differential expression of genes in signal transduction pathway (STP) during the hepatocarcinogenesis in tree shrews induced by AFB1 and/or HBV and to elucidate the molecular mechanism of hepatocellular carcinoma (HCC) development. METHODS: Adult tree shrews were divided into three groups: Group A was fed AFB1 only, Group B was infected firstly with HBV then fed AFB1 as in Group A, Group C served as the normal control. Liver biopsies were obtained at the 30th, 60th and 90th week of the experiment or until HCC occurred and the animals were sacrificed. Tree shrew-specific cDNA microarray was applied for detecting the differential expression of corresponding genes in each group at different time points during the experiment, and real time RT PCR was applied to verify the results of the cDNA microarray. RESULTS: Genes of IGF-II, C-rel, and NF-kappaB2 were differentially expressed between para-cancerous tissues and HCC tissues in both group A and group B, and the differential expression of bcl-2, cyclin A and CNTF was only seen in group B. Between the experimental groups A and B and the control group C, there were differential expressions of CNTF and cyclin A in the early 30th week and middle 60th week stage of hepatocarcinogenesis in tree shrews. Real time RT PCR results showed that the expression level of IGF-II and C-Rel in group A and of IGF-II in group B in HCC tissues were significantly lower than that in the adjacent non-cancerous tissues and in the biopsies taken at the 30th and 60th week of the experiment. Nevertheless, there were no significant differences between the para-cancerous tissues and the cancer tissues at the 30th and 60th week. These results were consistent with the cDNA microarray assay. The expression levels of C-Rel and CNTF in group B were not obviously altered in the para-cancerous tissues, HCC and at the 60th week, but they were significantly lower in these tissues than that in the tissues at the 30th week. In group A, the expression levels of CNTF in adjacent liver and HCC tissues were higher than that in para-cancerous lesions, but the difference did not reach a statistically significant level. In group C, the expression level of IGF-II, C-Rel and CNTF at different stages showed no significant differences, which was consistent with the cDNA microarray results. CONCLUSIONS: To apply the tree shrew-specific cDNA microarray to detect the differential expression of genes related to signal transduction pathway during tree shrew hepatocarcinogenesis could be a valuable utility for further comprehending the mechanism of HCC. IGF-II, NF-kappaB2, C-rel, Bcl-2, and cyclin A. CNTF may be involved in the occurrence and progress of HCC in tree shrews.

Animals↗
PubMed1984

Louse infestations of tree shrews (Tupaia glis).

Nine adult tree shrews, Tupaia glis, recently imported from West Malaysia were visually examined for ectoparasites while under general anesthesia. Three shrews were infested by the sucking louse, Sathrax durus , and six shrews had louse ova belonging to this species; two shrews had neither lice nor ova. A total of 20 adult female, 10 adult male, and three third instar nymphal lice was collected. Lice were located on the head, flanks, and dorsal body of shrews while ova were recorded mainly from the anterior flanks but also from some adjacent host sites. The tree shrews appeared to tolerate the lice well although louse vector capacity was not assessed. The last date that lice were recorded from shrews was 22 days after colony set-up, and the last date on which seemingly viable ova were recorded was 64 days after set-up showing that the infestations were ultimately lost.

Animals↗
PubMed1990

"Intermediate zone" of mammalian spleens: light and electron microscopic study of three primitive mammalian species (platypus, shrew, and mole) with special reference to intrasplenic arteriovenous communication.

The intermediate zone (IZ) of nonperfused and perfused spleens in three species of primitive mammals (shrew, mole, platypus) was studied morphologically. The IZ is a tissue zone consisting of plexiform vessels, probably venous capillaries, and is located transitionally between the white and red pulp. The IZ is separated from the white pulp by the arterial net (AN), in which the white pulp arteries terminate. Development of the IZ differs between the three species examined being distinctive in the platypus and shrew. The IZ is thin in the mole spleen. A closed type of arteriovenous (A-V) anastomosis was demonstrated in or around the IZ in the two Insectivora species examined. In the shrew spleen, peripheral arterial branches running within the IZ anastomose with the AN around the follicle. The AN anastomoses eventually with venous plexiform vessels of the IZ around the nonfollicular area of the white pulp to form a closed system. In the mole spleen, A-V anastomoses were noted between white pulp arteries (follicular and AN) and veins of the red pulp, either by direct communication or through fenestrated IZ vessels compatible with the plexiform vessels of the shrew spleen. A-V anastomosis in the IZ is probable, but not confirmed, in the platypus spleen, as analysis was limited to a nonperfused specimen. Well-developed ellipsoids were noted around arterial terminals of the IZ in the shrew spleen. Ellipsoids were also noted around all arterial terminals of the mole spleen directed to the red pulp. Most ellipsoids of the mole spleen appeared located within the IZ. No ellipsoids were present around arterial terminals of the IZ in the platypus spleen. Closed circulation was noted in terminals of the pulp artery in spleens of all three species. All pulp arteries of the mole spleen are postellipsoid segments of white pulp (AN and follicle) arteries. No ellipsoids were found around terminals of the pulp artery (penicillar artery) in shrew and platypus spleens. The IZ is probably homologous to the perilymphatic sinusoid (vein) of the lungfish spleen and may be regarded as part of the red pulp. The IZ may be representative of primitive mammalian spleens that have closed circulation. The marginal zone (MZ) of common mammalian spleens is probably a modified IZ by differentiation (remodelling) of the intrasplenic vein. In this process, withdrawal of venous vessels from the IZ occurred, leaving a lymphoreticular zone with open circulation (MZ). The marginal sinus reported in some mammalian spleens is probably a modified AN formed during this process. Possible morphological alterations of the spleen in vertebrate phylogeny are discussed.

Animals↗
PubMed1993

Esophageal carcinoma in house musk shrews, Suncus murinus (Insectivora), induced by N-methyl-N'-nitro-N-nitrosoguanidine.

Female 6-week-old shrews were given a solution of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at a concentration of 50 micrograms/ml or 100 micrograms/ml in the drinking water. All 11 shrews receiving 100 micrograms/ml MNNG died 8-13 days after the beginning of carcinogen administration and 6 of the 20 shrews receiving 50 micrograms/ml MNNG died after 10-54 days. When animals were between 43 and 54 weeks of age, multiple esophageal lesions were evoked in all 14 that had received 50 micrograms/ml MNNG for 30 weeks. All shrews developed a protruding, ulcerative, or superficial type of squamous-cell carcinoma of the esophagus, accompanied by papillomas. Local invasion was seen in squamous-cell carcinoma but no distant metastasis was noted. None of the 5 control shrews developed any esophageal abnormality. No gastric adenocarcinoma, intestinal sarcoma, or other tumors were induced with MNNG. It can be concluded that MNNG has a carcinogenic effect on shrew esophageal epithelium.

Animals↗