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At least 19 recordsLinked to original sources

PubMed1992

Maximum heart rate of soricine shrews: correlation with contractile properties and myosin composition.

Maximum heart rates (HR) of three soricine shrews and six other small mammals were measured in response to a single supramaximal dose of isoproterenol (Iso) under urethan anesthesia. The highest HR, 1,043 +/- 66 (SD) beats/min (n = 3), was in least shrew (Sorex minutus, mean body mass 3.02 +/- 0.81 g). Maximum HRs of common shrew (Sorex araneus, 7.16 +/- 1.54 g) and water shrew (Neomys fodiens, 12.80 +/- 1.54 g) were 938 +/- 29 (n = 7) and 887 +/- 21 (n = 6), respectively. In general, maximum HRs of soricine shrews and other small wild mammals followed the common mammalian pattern, fHmax/Iso = 443 x Mb-0.14, determined by body size. The exponent for this equation is smaller than that of resting HR (-0.25) (Stahl, J. Appl. Physiol. 22: 453-460, 1967), predicting crossover at approximately 3 g body mass. However, resting HRs of small mammals were clearly lower than expected on the basis of body mass. Lowering resting HR below the common mammalian level, with concomitant increase in stroke volume, seems to be a prerequisite for small mammals to regulate cardiac output against the ceiling of maximum HR. Electrophoretic analysis showed that the myosin of shrew ventricles is different from those of rodent species. In native conditions, shrew myosin, designated V1', migrated faster than the V3 and V1 forms of rat heart. On SDS gradient gel the single heavy chain of shrew myosin migrated slower than the alpha- or beta-chains of rat ventricle. Differences in the molecular weight of light chains were also noted between small mammals. Despite the notable differences in myosin composition, myosin-ATPase activity of the shrew hearts was similar to that of mouse and rat heart. Because duration of isometric contraction was inversely related to resting and maximum HRs, it was concluded that in the small mammals rate and duration of contraction are determined mainly by the release and uptake rate of myoplasmic Ca2+ and less by myosin-ATPase activity.

Animals↗

PubMed1992

Magnificent expression of asialo GM1 on thymus cells and spleen T cells of the musk shrew, Suncus murinus.

The expression of asialo GM1 (GA1) was observed on almost all thymocytes from young musk shrew, at the age of 4 weeks by flow cytometric analysis. In adult shrew aged 10 months, the ratio of GA1-negative thymocytes was increased. Among several anti-glycolipid antibodies used, anti-GM1 and anti-Forssman also reacted with the thymocytes. Protein fraction of the thymocytes was analyzed by SDS-PAGE followed by immunoblotting. Anti-GA1 and anti-GM1 showed two bands and one band, respectively, however, their mobilities were different from each other. Anti-Forssman did not stain any protein. The GA1-positive population in spleen T cell fraction was not detected in young shrew but most of the T cells were changed to GA1-positive cells in adult shrew. When mixed lymphocyte culture was performed, the GA1-negative spleen T cells in young shrew were changed to express GA1 marker on their cell surface by differentiation. Abbreviations used were as follows: GA1, Gal beta 1-3GalNAc beta 1-4Gal beta 1-4Glc-Cer; GM1, Gal beta 1-3GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta 1-4Glc-Cer; Forssman, GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-Cer.

Animals↗

PubMed1992

Intestinal disaccharidases in the house musk shrew, Suncus murinus: occurrence of sucrase deficiency.

1. Disaccharidase activities of the small-intestinal brush border membrane were studied in six laboratory lines of the house musk shrew, Suncus murinus. 2. Sucrase activity was detected in all shrews of one line, but not in any shrew of three lines. In the other two lines it was found in some shrews, but not in the others. 3. Maltase, isomaltase, trehalase and lactase activities were found in all shrews of all the lines examined. 4. Sucrase was normally associated with isomaltase to form an enzyme complex. 5. Detergent-solubilized isomaltase, whether associated with sucrase or not, was inhibited by antibodies against rabbit sucrase-isomaltase to almost the same extent as the rabbit one, suggesting that isomaltase is not affected by a mutation(s) in sucrase.

Animals↗

PubMed1992

Inheritance and breeding of the waltzing mutant in the musk shrew (Suncus murinus, Insectivora) characterized by the circling and head-shaking behaviors.

A behavioral mutant was found in the laboratory-bred musk shrew (Suncus murinus). The affected shrews were characterized by the behaviors of tight circling in both directions and frequent head shaking in horizontal. They could definitely be identified by at least day 10 after birth. These abnormal behaviors were steady and permanent through life. Mating experiments demonstrated that the mutant character is expressed by a single autosomal recessive gene in homozygote with complete penetrance. The pedigree analysis indicated that the gene was derived from one heterozygous male captured in Ginowan city, Okinawa. The name, waltzing, was proposed for this mutant character with the gene symbol wz. An abnormality of the balance organ was predicted for a cause of the abnormal behaviors, since, besides the circling and head shaking behaviors, the affected shrews could not keep the body stretching but twisted it frequently when they were held up by the tail and further they could not keep the head on the water surface at all. Nevertheless, the affected shrews were almost normal in gestation period, litter size, weaning ratio and body weight in comparison with the phenotypically normal ones. The mutant shrews have been maintained as a closed colony, the WZ line involved more than 30 individuals at every one generation.

Animals↗

PubMed1992

Neural distribution of estrogen receptor immunoreactive cells in the female musk shrew.

In this report we describe the neural distribution of estrogen receptor immunoreactivity (ER-IR) in the female musk shrew (Suncus murinus). The highest concentrations of neurons containing ER-IR were found in the preoptic areas, the lateral septum, the anterior arcuate and ventromedial nuclei of the hypothalamus, the medial nuclei of amygdala, and the midbrain central grey. Additional preoptic, hypothalamic, limbic and midbrain nuclei also contained ER-IR cells. The distribution of ER-IR was similar to that described in other mammals and birds, with several important differences. In the female musk shrew, there was little difference in ER-IR intensity or distribution when brains from gonadally intact and ovariectomized musk shrews were compared. In addition, long-term treatment with a supraphysiological dose of estradiol was required to detect a decrease in ER-IR intensity. Finally ER-IR was noted in both nuclear and cytoplasmic regions of cells in ovariectomized and gonadally intact musk shrews. The dense ER-IR noted in intact females as well as the presence of cytoplasmic stain may be due to the unusual relationship between estradiol, ovulation and sexual receptivity in this species.

Animals↗

PubMed1992

Red-eyed dilution (rd), a novel coat-color mutant gene in the musk shrew (Suncus murinus, Insectivora).

A novel coat-color mutant was found in the musk shrew (Suncus murinus). Mutant shrews were characterized by light-gray coat, pinkish skin and red eyes. Mating experiment demonstrated that the mutant character was controlled by a single autosomal recessive gene. The gene could be traced back to at least four heterozygous carriers captured in Naha city, Okinawa in 1983. The name, red-eyed dilution, was proposed for this mutant character with the gene symbol rd. Linkage analysis proved no close relationship of the rd locus with the cr (cream coat color) and ch (curly hair) loci. The red-eyed dilution shrews (+/+, rd/rd) could easily be distinguished from the cream coat shrews with dark-red eyes (cr/cr, +/+) and the double homozygotes exhibiting light-cream coat with pink eyes (cr/cr, rd/rd). The rd gene has been maintained in the OKI line about at 75% of its frequency in every generation. We have started to develop a new line triple-homozygous for the cr, ch and rd genes.

Animals↗

PubMed1979

The occurence of coxiellosis among rodents and shrews in the Tarai area of Uttar Praedesh.

Rodents and shrews were screened for serologic evidence of Coxiella burnetii. Attempts were made to isolate the organism from the spleen and liver. Seroreactors: total positive/total tested (% positive), in rats (Rattus rattus, R. norvegicus), ground shrews (Suncus murinus), bandicoots (Bandicota indica, B. bengalensis) and the house mouse (Mus musculus), respectively, were 13/105 (12.38), 6/42 (14.3), 2/15 (13.3) and 1/7 (14.3). Of the eight rickettsial isolants recovered including four from field and household rats, three from ground shrew and one from bandicoots, only three comprising one each from rat, shrew and bandicoot, could be typed as C. burnetii. This appears to be the first record of rodents and an insectivore as reservoirs of C. burnetii in India.

Animals↗

PubMed1976

Induction of liver tumors by aflatoxin B1 in the tree shrew (Tupaia glis), a nonhuman primate.

The epidemiological studies suggest that aflatoxins, the toxic metabolites of the ubiquitous mold Aspergillus flavus, may play a significant role in the evolution of hepatocellular carcinoma in man in certain geographic areas of the world. To ascertain their carcinogenicity in nonhuman primates, we have administered highly purified aflatoxin B1, intermittently in the diet at 2 ppm, to 10 female and 8 male tree shrews. The tree shrew (Tupaia glis) is a nonhuman primate occurring throughout Southeast Asia which can be reared easily in captivity. Of 12 animals that survived, 6 of 6 female (100%) and 3 of 6 male (50%) tree shrews developed hepatocellular carcinomas between 74 and 172 weeks after the beginning of the experiment. None of the 8 control animals developed liver cancers. The estimated total amount of aflatoxin B1 consumed by these animals ranged from 24 to 66 mg. The development of liver tumors did not follow a specific pattern; considerable variation in hepatocellular responses to aflatoxin B1 was noted in these animals. In 2 tree shrews, the liver tumors were associated with severe post necrotic scarring; in the other 7 tumor-bearing livers, only mild to moderate portal fibrosis was encountered. This individual variation in hepatocellular response and in the amount of aflatoxin B1 required to induce hepatocellular carcinomas is attributed to inherent differences in the susceptibility within a given species of outbred animals and suggests extreme caution in proposing the "permissible" or "safe" levels of contamination of carcinogens in the food-stuffs.

Aflatoxins↗

PubMed1992

Distribution of gonadotrophins within the anterior pituitary cells of the musk shrew (Suncus murinus L.).

Gonadotrophs in the anterior pituitary gland of the musk shrew were first identified by means of electron microscopic immunocytochemistry. The gonadotrophs of the musk shrew revealed quite unusual ultrastructural features that have never been seen before in other species. These cells contained two types of secretory granules, i.e., small dense, round-shape granules and large lucent, irregular-shape granules. FSH beta and LH beta were mostly observed together on both small and large secretory granules. The distribution pattern of the subunits of gonadotrophs was slightly altered following gonadectomy in the musk shrew.

Animals↗

PubMed1992

Male common shrews (Sorex araneus) with long meiotic chain configurations can be fertile: implications for chromosomal models of speciation.

Two chromosomal races of common shrews (Sorex araneus) were crossed in captivity to generate chain VII-forming complex Robertsonian heterozygotes. Meiosis and gametogenesis were studied in three male hybrids. Regular chain VII configurations were observed at both pachytene and diakinesis/metaphase I, although in many pachytene spreads the chain configuration was incomplete (the basis of this peculiarity is unknown). From metaphase II counts, the frequency of anaphase I nondisjunction in the complex heterozygotes was estimated to be 13%. Germ-cell death in the chain VII-forming complex heterozygotes was 22% greater than it was in controls, but this difference is unlikely to have greatly influenced the capacity of the heterozygotes to sire offspring. Thus, the fecundity of these complex heterozygous common shrews would probably have been only slightly reduced relative to homozygous or simple heterozygous shrews. These results call into question the generality of speciation models based on the presumed sterility of complex heterozygotes.

Animals↗

PubMed1992

Kinky coat, a new autosomal recessive mutation in the musk shrew, Suncus murinus.

A kinky-coat mutant was discovered at the fifth generation of the BAN strain originating from wild musk shrews (Suncus murinus) in Bangladesh. Mating experiments indicated that the kinky-coat character is controlled by a single autosomal recessive gene designated kc (kinky coat), which is not allelic to the gene ch (curly hair) previously reported in the Tr strain derived from wild musk shrews on Taramajima Island, Japan. Because the kc/kc homozygotes were fully fertile and viable, the kc gene should be useful as a genetic marker in linkage studies. In external appearance, homozygotes were characterized by curly vibrissae, somewhat unkept coat hair, and wavy long hair on the tail. Both the length and width of coat hair did not differ significantly between homozygous and normal shrews. Light microscopic observations showed that shafts of the kc coat hair are wavy and often have small swellings with disorganization of the medullary structure. Scanning electron microscopic examinations further revealed that the shafts of the vibrissae, coat hair, and tail hair have abnormalities such as longitudinal fissures, twists, and hollows. It is clear that these modifications caused waviness or curling of the shafts of the three kinds of hairs observed.

Alleles↗

PubMed1992

Morphological study of parafollicular cells and the parathyroid gland in the house shrew (Suncus murinus).

A morphological study of parafollicular cells in the thyroid gland and parathyroid gland of the house shrew (Suncus murinus) was made. The results indicated that (1) there were two pairs of parathyroid glands which were located in the upper part of the house shrew thyroid gland, (2) the volumes of the house shrew parathyroid glands ranged from 0.014 to 0.079 mm3, (3) the number of parafollicular cells along the follicles was largest in the upper part of the thyroid lobe, while no parafollicular cells were present in the isthmus, and (4) there were about 20 parafollicular cells per 100 follicular cells and 1.519 parafollicular cells per follicle. The number of parafollicular cells per 100 follicular cells was thus about 5 times larger than that in rats and the number of parafollicular cells per follicle about 2.5 times larger than that in rats.

Animals↗

PubMed1978

[Population of hair cells in the Corti's organ of shrews].

In shrews (family Soricidase) the organ of Corti was examined by means of the surface specimen technique. The analysis of the qualitative deviations from the normal cellular pattern of Corti organ was based on more than 160 ears of shrews (Sorex araneus, S. minutus, Neomys fodiens, and Crocidura suaveolens). The dislocation, rotation, malformation of hair cells, and one finding of the giant outer hair cell are described. The quantitative analyses of the population of hair cells are based on 61 ears of Sorex araneus divided into 2 age groups. The mean values of aplasias and of missing and supernumerary hair cells in dependence on individual rows and half-turns of cochlea are given. The loss of hair cells depends on the age of the animal. The findings of aplasias and supernumerary outer hair cells (especially those of atypical 4th row) are relatively frequent in shrews. The organ of Corti in shows has a very regular arrangement; deviations of all types are scant and thus we may hold the ideal cochleogram for the norm. The found deviations seem to have no functional meaning.

Age Factors↗

PubMed1992

Immunohistochemical organization of the ventral lateral geniculate nucleus in the tree shrew.

The ventral lateral geniculate nucleus (vLGN) of the tree shrew (Tupaia belangeri) was differentiated into multiple subdivisions (dorsal cap, intergeniculate leaflet, parvicellular segment, and internal and external magnocellular laminae, the latter being further divisible into a lateral and medial division) on the basis of retinal projections, immunochemistry, and histochemistry. Retinal projections traced with intravitreal injections of wheat germ agglutinin conjugated horseradish peroxidase revealed direct bilateral input to all subregions of the vLGN, except for the internal magnocellular lamina (which received only contralateral input) and the parvicellular segment (which was not retinorecipient). Furthermore, retinal inputs clearly distinguished the relatively heavily retinorecipient intergeniculate leaflet from the less prominently labeled dorsal cap. Immunohistochemical localization of Neuropeptide Y (NPY) perikarya revealed their prominence in the intergeniculate leaflet and the external magnocellular laminae with a concentration along the optic tract. NPY immunoreactive fibers were seen in all but the parvicellular subregion. Gamma amino butyric acid immunoreactivity was seen throughout the vLGN, but was most concentrated in the dorsal cap and the magnocellular laminae, followed by the intergeniculate leaflet. Histochemical studies of cytochrome oxidase and nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase localization revealed similar patterns of dense reactivity within the external magnocellular lamina, intergeniculate leaflet and dorsal cap, and somewhat less dense, but substantial reactivity in the internal magnocellular lamina. Within the external magnocellular lamina, cells reactive for cytochrome oxidase were noted in the lateral portion bordering the optic tract, whereas those specific for NADPH-diaphorase were dispersed throughout the lamina. Poor reactivity for both histochemical markers was evident in the parvicellular segment. Overall, the markedly different patterns of retinal input and neurochemical organization between the subdivisions of the tree shrew vLGN suggest their involvement in diverse functions. Furthermore, the basic similarity of the organization of the tree shrew vLGN to that of the taxonomically unrelated ground squirrel may indicate a common mammalian scheme.

Animals↗

PubMed1978

The annular hematoma of the shrew yolk-sac placenta.

The annular hematoma of the shrew, Blarina brevicauda, is a specialized portion of the yolk-sac wall. In this study, we have examined the fine structure of the different cellular components of the anular hematoma. Small pieces of the gestation sacs from seven pregnant shrews were fixed in glutaraldehyde and osmium tetroxide and processed for transmission electron microscopy. In the area of the trophoblastic curtain, the maternal capillary endothelial cells were hypertrophied and syncytial trophoblast surrounded the capillaries. Cellular trophoblast covered part of the luminal surface of the curtain region, whereas masses of apparently degenerating syncytium were present on other areas of the surface. Maternal erythrocytes, released into the uterine lumen from the curtain region, were phagocytized and degraded by the columnar cells of the trophoblastic annulus. No evidence of iron or pigment accumulation was evident in the parietal endodermal cells underlying the annular trophoblast. Parietal endodermal cells were characterized by cuboidal shape, widely dilated intercellular spaces, and cytoplasm containing granular endoplasmic reticulum. Endodermal cells of the visceral yolk-sac accumulated large numbers of electron-dense granules as well as glycogen in their cytoplasm. Hemopoietic areas and vitelline capillaries were found subjacent to the visceral endoderm. The various portions of the yolk-sac wall of Blarina appear to perform complementary functions which are probably important in maternal-fetal iron transfer.

Animals↗

PubMed1992

Ultrastructural study of postnatal development of the tonsillar crypt epithelium of the musk shrew, Suncus murinus.

An ultrastructural study was made of the postnatal development of the tonsillar crypt epithelium in the musk shrew, Suncus murinus. On day 3 after birth, a particular kind of large lymphoid cell was first seen to move through the basement membrane into the epithelium. The next migration was that of lymphocytes, which passed through holes in the basement membrane. On days 5 to 7, the lymphocytes formed clusters, and pale epithelial cells of low electron density appeared. The cell clusters and pale epithelial cells fused on day 10. By day 14, these epithelial cells extended cytoplasmic projections to the surface of the epithelium, which had many heterophagic vacuoles and some microvilli-like structures. These findings suggest that the lymphoepithelial relationship is important for the organization of the immunological microenvironment in tonsillar crypt epithelium of the neonatal musk shrew.

Animals↗

PubMed1992

Effects of estradiol valerate on the uterus of the musk shrew (Suncus murinus L.).

The effects of exogenous estradiol valerate on some uterine characteristics of the musk shrew were investigated. Treatment with the steroid for either 1 day or 7 days did not noticeably alter luminal epithelial cell height, endometrial gland epithelial cell height or diameter, or number of endometrial glands. The reciprocal values of cell density of circular muscle and deep endometrial layers and endometrium-to-myometrium ratio of the uterus increased significantly in response to 7 days of steroid administration. After 1 day of steroid treatment the numbers of mast cells in different layers of the uterus (i.e., meso-, myo-, and endometrium) were unchanged, but after 7 days there were significant increases in the number of mast cells in meso- and myometria. The number of eosinophils in all three layers of the uterus increased significantly in response to the treatment of estradiol for 1 day or for 7 days. The increase was greater in the 7-day group. Neither uterine DNA nor RNA contents changed following administration of the steroid for either group, although protein content was elevated significantly in the 7-day group. Estradiol administration thus evokes small but subtle changes in the uterus of the musk shrew.

Animals↗

PubMed1992

Adrenal contribution to the induction of sexual behavior in the female musk shrew.

Sexually experienced female musk shrews (Suncus murinus) lack an ovarian, vaginal, and behavioral estrous cycle. Females, once induced by their initial contact with a male, are able to display copulatory behavior whenever a male is present (Rissman, Silveira, and Bronson, 1988). Based on plasma levels of steroids, and on hormone replacement studies conducted after ovariectomy (OVX), we have shown that testosterone (T) plays an essential role in the regulation of female sexual behavior (Rissman and Crews, 1988; Rissman, Clendenon, and Krohmer, 1990a; Rissman, 1991). To date we have only examined the potential contribution of adrenal steroids to female sexual behavior in a preliminary manner. After adrenalectomy, gonadally intact females display significantly lower levels of sexual behavior than controls (Rissman and Bronson, 1987). The following experiments were conducted to examine the role the adrenal steroids (in contrast to the medullary hormones) play in the induction of female sexual behavior in the musk shrew. In the first experiment gonadally intact females were treated with dexamethasone (DEX) to reduce the secretion of adrenal steroids. Significantly fewer females receiving DEX demonstrated sexual behavior as compared with controls. In the second study, OVX females received T-filled Silastic implants. When DEX was administered to OVX + T females at a dose that dropped circulating T levels to those found in ovary and adrenal intact females, no effect on sexual behavior was noted. The data show that the adrenals are a behaviorally important source of T and contribute toward the hormonal control of sexual behavior in these female mammals.

Adrenal Glands↗