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At least 19 recordsLinked to original sources
PubMed1996

Phylogenetic relationships within caniform carnivores based on analyses of the mitochondrial 12S rRNA gene.

The complete 12S rRNA gene of 32 carnivore species, including four feliforms and 28 caniforms, was sequenced. The sequences were aligned on the basis of their secondary structures and used in phylogenetic analyses that addressed several evolutionary relationships within the Caniformia. The analyses showed an unresolved polytomy of the basic caniform clades; pinnipeds, mustelids, procyonids, skunks, Ailurus (lesser panda), ursids, and canids. The polytomy indicates a major diversification of caniforms during a relatively short period of time. The lesser panda was distinct from other caniforms, suggesting its inclusion in a monotypic family, Ailuridae. The giant panda and the bears were joined on the same branch. The skunks are traditionally included in the family Mustelidae. The present analysis, however, showed a less close molecular relationship between the skunks and the remaining Mustelidae (sensu stricto) than between Mustelidae (sensu stricto) and Procyonidae, making Mustelidae (sensu lato) paraphyletic. The results suggest that the skunks should be included in a separate family, Mephitidae. Within the Pinnipedia, the grouping of walrus, sea lions, and fur seals was strongly supported. Analyses of a combined set of 12S rRNA and cytochrome b data were generally consistent with the findings based on each gene.

Animals↗
PubMed1996

Progression of trophoblast into the endometrium during implantation in the western spotted skunk.

BACKGROUND: In mustelid carnivores, several blastocysts become implanted either approximately 12 days following fertilization or after a delay of implantation. In the western spotted skunk, implantation occurs following a long period of delayed implantation and a brief activation stage. Within each implantation chamber, a large number of trophoblastic plaques form, and the syncytial trophoblast of these plaques adheres to and penetrates into the uterine luminal epithelium. The presence of multiple attachment sites was used to analyse the way in which trophoblast adheres to, penetrates, and removes uterine epithelium and its subsequent association with the subepithelial vascular plexus. METHODS: Implantation chambers from 18 western spotted skunks were collected during the first week postimplantation and the tissue prepared for light microscopy and scanning and transmission electron microscopy. RESULTS: A series of trophoblastic plaques, which form a ring peripheral to the embryonic shield, attach to and penetrate the uterine epithelium. As new trophoblastic plaques are forming, the initial plaques enlarge and spread along the basal lamina of the luminal epithelium, and trophoblastic processes project through this basal lamina. Subsequently there is a stage of consolidation in which cytotrophoblast increases greatly in amount, attachment sites coalesce, and the luminal epithelium is eliminated. Syncytial trophoblast intrudes into endometrial gland lumina and surrounds subepithelial capillaries. CONCLUSIONS: It is suggested that the affinity of syncytial trophoblast for apical junctional complexes of uterine epithelial cells facilitates intrusion of syncytial trophoblast between cells, possibly guided by the marginal ridges of the uterine cells. The trophoblast shows no tendency to adhere to or invade maternal capillaries. This lack of adhesion to endothelial cells suggests either a change in adhesive properties of trophoblast following epithelial penetration or differences in adhesive properties between surface epithelial cells and endothelial cells. Although trophoblast differentiation appears to be chronologically regulated, it could be responding to maternally derived factors.

Animals↗
PubMed1976

Morphological changes in the trophoblast, uterus and corpus luteum during delayed implantation and implantation in the western spotted skunk.

Morphological interactions of tropholbast and uterus from stages of preimplantation and implantation were studied in 14 western spotted skunks. In addition, the granulosa lutein cells and plasma progesterone levels were studied. In animals several days from implantation the height of epithelial cells decreased, but began to increase in animals approaching implantation. During the preimplantation period a few leucocytes infiltrated the epithelium, but in animals just prior to implantation many leucocytes infiltrated the epithelium.

Animals↗
PubMed1978

Induced ovulation, development of the corpus luteum, and tubal transport in the striped skunk (Mephitis mephitis).

Ovulatory pattern, development of the corpus luteum (CL), and early tubal transport are described for 6 unmated and 19 mated striped skunks (mephitis mephitis) killed after known copulation times. Ovulation is induced by copulation and occurs around 42 hours (range = 40--50 hours) after first insemination. Seventeen of 19 females killed between 36 hours and 19 days postcoitus had ovulated. Two females killed at 36 hours had not ovulated; however, their follicles showed preovulatory changes and were significantly larger (p less than 0.01) than those of unmated females. Six unmated females, killed during and three weeks after the normal breeding season, had not ovulated. Ovarian events, such as preovulatory changes, ovulation, and development of the corpus luteum (CL), are described for animals killed 36 hours to 19 days post-coitus. Maximum CL size occurred at 11 days post-coitus and coincided with the onset of embryonic migration and enlargement. Embryonic development reflected individual variation in ovulation times. The first polar body was extruded at ovulation and the second at fertilization. Pronuclear stages were predominant at 42 to 48 hours and 3 to 8-cell stages at 72 to 96 hours; morulae (containing up to 95 cells) entered the uterus at seven days. Blastocysts were observed first at 11 days when embryonic spacing and enlargement began. Implantation occurred by 19 days.

Animals↗
PubMed1985

Accumulation of RNA in blastocysts during embryonic diapause and the periimplantation period in the western spotted skunk.

The in vivo incorporation of 3H-uridine into RNA was studied in delayed implanting and activated blastocysts obtained from 33 western spotted skunks. 3H-uridine was incorporated into RNA by all blastocysts; however, significantly more label was incorporated as blastocyst diameter increased. Activated blastocysts with diameters of 1.6 mm or greater on average incorporated 65 times more 3H-precursor in 5 hr than diapausing blastocysts with diameters of 1.1 mm or less. Polyadenylated RNA was likewise synthesized by delayed implanting and activated skunk blastocysts; however, the proportion of polyadenylated RNA synthesized by the former was greater than in the latter (43.9% vs. 27.5%). Our data suggest that the transition from embryonic diapause to fully activated blastocysts first occurs gradually for several days before entering a 1-2-day period of rapid development characterized by an abrupt increase in RNA accumulation.

Animals↗
PubMed1990

Testicular response to melatonin or suprachiasmatic nuclei ablation in the spotted skunk.

Testes of the Western spotted skunk enlarge and regress seasonally. The pineal hormone, melatonin, may be important in timing this seasonal reproductive activity. Likewise, the suprachiasmatic nuclei (SCN) have been implicated as possible neural regulators of pineal and reproductive events. These experiments were conducted to determine whether ablation of the SCN or constant administration of melatonin alters timing of the seasonal pattern of testicular regression and recrudescence. Male skunks (n = 24) were treated as follows: six received two empty Silastic capsules, six received two melatonin-filled Silastic capsules, six received sham lesions to the SCN, and six received lesions to the SCN (SCNx). All skunks were exposed to a natural photoperiod and had regressed testes at the onset of the experiment. Four of six males from the SCNx group had an average of 94 +/- 11.3% of these nuclei destroyed. Sham SCNx, animals with less than 40% of the SCN ablated, and males with empty capsules did not have fully enlarged testes until October. SCNx and melatonin-treated skunks exhibited a hastening of testicular recrudescence with maximal testis size being reached in June. Skunks with lesions to the SCN maintained enlarged testes for 5 months while all other groups exhibited rapid regression after attaining maximal testis size. Testicular regression occurred from July through October in animals receiving continuous melatonin, while controls exhibited recrudescence during this same period. Our data suggest that the SCN, melatonin, and thus the pineal gland, play a role in regulating the seasonal testicular cycle of the spotted skunk.

Analysis of Variance↗
PubMed1993

Effect of melatonin on pituitary secretion of prolactin in vitro during delayed implantation and the periimplantation period in the spotted skunk.

The pars tuberalis of the western spotted skunk is the only region of the brain known to bind 2-[125I]iodomelatonin, thus suggesting that this region of the pituitary might be essential in mediating the effects of melatonin in this species. Female skunks were killed during short- and long-day photoperiods. Hemisections of the adenohypophysis, with and without the pars tuberalis were cultured in the presence and absence of 10 nM melatonin to determine whether the pars tuberalis mediates the previously observed suppressive effects of melatonin on the seasonal increase in plasma prolactin levels in this species. Pituitaries obtained during long-day photoperiods secreted significantly more prolactin than those obtained during the short-day photoperiod. Melatonin had no effect on pituitary response to gonadotropin releasing hormone and failed to inhibit prolactin secretion during the 48 h culture period. However, melatonin significantly reduced the inhibitory effects of dopamine on prolactin secretion. The latter response was observed in both photoperiods and in the presence and absence of the pars tuberalis. These results suggest that the pars tuberalis does not mediate the inhibitory effect of melatonin on prolactin secretion in the absence of the hypothalamus.

Animals↗
PubMed1995

Characterization of a human adenovirus 5: rabies glycoprotein recombinant vaccine reisolated from orally vaccinated skunks.

An infectious recombinant human adenovirus which carries the rabies glycoprotein gene and accompanying SV40 control elements can be given orally to skunks to immunize them against rabies. We have looked for adenovirus in the feces and oral fluids of animals that have been given this recombinant and have obtained 111 virus positive samples from 16 test animals. DNA from these virus isolates was examined for possible mutations. One possible insertion mutation was detected by SmaI restriction endonuclease analysis of genomic DNA. Further analysis by HaeIII restriction and nucleotide sequencing of polymerase chain reaction products encompassing the whole SV40-rabies insert revealed that this isolate contained an insert of the 72 base pair sequence found in the SV40 promoter region. A second mutation, in which 54 base pairs were deleted from within the rabies glycoprotein gene, was also detected in two independent isolates from one skunk.

Adenoviruses, Human↗
PubMed1975

Ultrastructural changes in granulosa lutein cells and progesterone levels during preimplantation, implatation, and early placentation in the western spotted skunk.

The ultrastructure of corpora lutea obtained during the preimplantation implantation and early post-implantation periods has been studied in 20 western spotted skunks. Fine structure of granulosa lutein cells was correlated with progesterone levels. The corpus luteum of the prolonged (7 month) preimplantaion period contained undifferentiated small granulosa cells and differentiated large granulosa lutein cells. The former ranged in size between 12 and 20 mu and the latter between 20 and 45 mu. The ratio of small and large cells was about equal in an animal 2 days prior to nidation whereas only few small cells and numerous large cells were observed in an animal estimated to be 8 to 12 hours from nidation. Occasionally small cells were observed amidst large ones during the 24 hour nidation period, i.e. adhesion of trophoblast with the luminal uterine epithelium, but small cells were absent in animals after this period. Small cells had some smooth and rough endoplasmic reticulum rod-shaped mitochondria with plate-like cristae, small Golgi complex, and relatively smooth plasma membranes. Large lutein cells had abundant smooth endoplasmic reticulum, membranous whorls of smooth endoplasmic reticulum, usually round mitochondria with tubular and lamellar cristae, a well developed Golgi complex, variable amounts of lipid droplets, and highly plicated and ruffled plasma membranes. Peripheral plasma progesterone levels during the prolonged preimplantation period ranged between 1.1 and 7.9 ng/ml, but during implantation it was between 8 and 16.6 ng/ml. It is suggested that plasma progesterone levels fluctuate during the time of implantation and should not be regarded as a basis to predict actual nidation in the western spotted skunk.

Animals↗
PubMed1992

The distribution of Challenge virus standard rabies virus versus skunk street rabies virus in the brains of experimentally infected rabid skunks.

The proposal that the bizarre behavioral changes which occur during rabies infection are due to selective infection of limbic system neurons was further studied in skunks (a species important in naturally occurring disease). A detailed immunohistochemical study of brains of skunks experimentally infected with either Challenge virus standard (CVS) or street rabies virus revealed only trace amounts of viral antigen in many limbic system neurons and marked differences in viral distribution between street and CVS virus. These data were collected during early stage rabies when behavioral changes occur. Areas which contained heavy accumulations of street rabies virus but low amounts of CVS rabies virus were the neuronal perikarya and processes of the dorsal motor nucleus of the vagus, midbrain raphe, hypoglossal and red nuclei. In contrast, large accumulations of CVS virus were found in the Purkinje cells of the cerebellum, the habenular nuclei and in pyramidal cells throughout the cerebral cortex, while corresponding areas in all street virus-infected skunks contained minimal antigen. These findings were very consistent for animals of the same experimental group and between skunks inoculated both intramuscularly and intranasally with skunk street virus. Skunks inoculated intramuscularly with CVS rabies virus failed to develop rabies. Since, in this model, street virus infection generally produces furious rabies and CVS infection results in dumb rabies, we speculate that the behavioral changes which occur in these two different clinical syndromes are due to the heavy and specific accumulation of virus in different regions of the CNS. These results show that regions other than those of the limbic system may also be involved in the pathogenesis of behavior changes in rabid animals.

Animals↗
PubMed1984

Rabies: spongiform lesions in the brain.

Striped skunks (Mephitis mephitis) experimentally infected with street rabies virus developed spongiform lesions that light- and electron-microscopically were indistinguishable from those found in the transmissible spongiform encephalopathies of man and animals. These previously unreported lesions were also detected in naturally occurring cases of rabies. The spongiform lesions consisted of round or oval vacuoles in the neuropil, rarely in neuronal perikarya. The most severely affected areas were the thalamus and cerebral cortex. The implications of this finding include similarities in the pathogenetic mechanisms of rabies and the traditional spongiform encephalopathies and the possibility of lesion variation due to differences in rabies viral strains. The spongiform lesions of rabies will require consideration in differential diagnosis.

Animals↗
PubMed1988

Comparison of spongiform lesions in experimental scrapie and rabies in skunks.

Striped skunks were inoculated intracerebrally with the scrapie agent (suspension of brain from a naturally infected Suffolk sheep) or intramuscularly with street rabies virus (suspension of salivary glands from naturally infected skunks). Those given the scrapie agent developed clinical signs of weakness, posterior ataxia, and emaciation after incubated periods of 8 to 23 months. Those inoculated with rabies virus developed clinical signs of rabies (aggressive behavior, hyperexcitability, ataxia and paralysis) after incubation periods of 20 to 62 days. The gross lesions in the brains of the skunks given the scrapie agent consisted of marked atrophy of the thalamus and moderate atrophy of the cerebrum. No gross lesions occurred in the rabid skunks. Histologically, the type of spongiform lesion in rabies was the same as that in scrapie. However, spongiform change of rabies infected brains was less extensive (only rarely affected the basal ganglia, hippocampus or hypothalamus) than that of brains infected with the scrapie agent and was characterized by fewer numbers of small vacuoles (as a proportion of total number of vacuoles) than occurred in scrapie spongiform change.

Animals↗
PubMed1992

Oral rabies vaccination of skunks and foxes with a recombinant human adenovirus vaccine.

A new recombinant rabies vaccine (human adenovirus 5 containing the rabies glycoprotein gene) was given to striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes). Groups of skunks received the vaccine in baits, by direct instillation into the mouth, or intramuscularly. Foxes were given vaccine by direct instillation into the oral cavity (DIOC). Selected groups of vaccinated skunks and foxes were challenged with street rabies virus. There were high rates of seroconversion (generally with high antibody titers) in both foxes and skunks, with survival of all challenged vaccinated animals (all challenge controls developed rabies). In skunks, vaccine given DIOC was effective over a broad range of doses (10(8.7), 10(7.6) and 10(6.4) median tissue culture infective doses). There was no evidence of pathogenic effects. The results indicate that this adenovirus recombinant has considerable potential as a wildlife oral rabies vaccine.

Adenoviruses, Human↗