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PubMed2006

Marine mammal neoplasia: a review.

A review of the published literature indicates that marine mammal neoplasia includes the types and distributions of tumors seen in domestic species. A routine collection of samples from marine mammal species is hampered, and, hence, the literature is principally composed of reports from early whaling expeditions, captive zoo mammals, and epizootics that affect larger numbers of animals from a specific geographic location. The latter instances are most important, because many of these long-lived, free-ranging marine mammals may act as environmental sentinels for the health of the oceans. Examination of large numbers of mortalities reveals incidental proliferative and neoplastic conditions and, less commonly, identifies specific malignant cancers that can alter population dynamics. The best example of these is the presumptive herpesvirus-associated metastatic genital carcinomas found in California sea lions. Studies of tissues from St. Lawrence estuary beluga whales have demonstrated a high incidence of neoplasia and produced evidence that environmental contamination with high levels of polychlorinated biphenols and dichlorophenyl trichloroethane might be the cause. In addition, viruses are suspected to be the cause of gastric papillomas in belugas and cutaneous papillomas in Florida manatees and harbor porpoises. While experimental laboratory procedures can further elucidate mechanisms of neoplasia, continued pathologic examination of marine mammals will also be necessary to follow trends in wild populations.

Animals↗
PubMed2006

Lack of patchy horizontal connectivity in primary visual cortex of a mammal without orientation maps.

In the cerebral cortex of mammals, horizontal connections link cells up to several millimeters apart. In primary visual cortex (V1) of mammals with orientation maps, horizontal connections ramify in periodic patches across the cortical surface, connecting cells with similar orientation preferences. Rodents have orientation-selective cells but lack orientation maps, raising questions about relationships of horizontal connections to functional maps and receptive field properties. To address these questions, we studied anatomy of horizontal connections and characterized horizontal functional interactions in V1 of the gray squirrel, a highly visual rodent. Long-range intrinsic connections in squirrel V1 extended 1-2 mm but were not patchy or periodic. This result suggests that periodic and patchy connectivity is not a universal organizing principle of cortex, and the existence of patchy and periodic connectivity and functional maps may be linked. In multielectrode and intracellular recordings, we found evidence of unselective local interactions among cells, similar to pinwheel centers of carnivores. These data suggest that, in mammals with and without orientation maps, local connections link near neighbors without regard to orientation selectivity. In single-unit recordings, we found length-summing and end-stopped cells that were similar to those in other mammals. Length-summing cell surrounds were orientation selective, whereas surrounds of end-stopped cells were not. Receptive field response classes are quite similar across mammals, and therefore patchy and columnar connectivity may not be essential for these properties.

Animals↗
PubMed2006

C-values of seven marine mammal species determined by flow cytometry.

C-values, which estimate genome size, have puzzled geneticists for years because they bear no relationship to organismal complexity. Though C-values have been estimated for thousands of species, considerably more data are required in order to better understanding genome evolution. This is particularly true for mammals, in which C-values are known for less than 8% of the total number of mammalian species. Among marine mammals, a C-value has been estimated only for the bottlenose dolphin (Tursiops truncatus). Thus examination of additional species of marine mammals is necessary for comparative purposes. It will enable a better understanding of marine mammal genome evolution, and it is also relevant to conservation, because larger genome size has been linked to increased likelihood of extinction in some plant and animal groups. Our study presents C-values of seven marine mammal species, including five cetacean species that are endangered to varying degrees. Similarly to the results for other groups, our results suggest that larger genome size in cetaceans is related to an increased likelihood of extinction.

Animals↗
PubMed1987

Antibody to Crimean-Congo hemorrhagic fever virus in wild mammals from southern Africa.

Crimean-Congo hemorrhagic fever (CCHF) virus is becoming increasingly recognized as an important human pathogen in southern Africa. In order to determine the role of wild mammals in the natural ecology of the virus, sera from 3,772 wild mammals of 87 species and from 1,978 domestic dogs collected in South Africa and Zimbabwe between 1964 and 1985 were tested for antibody to CCHF virus by reversed passive hemagglutination inhibition (RPHI) and by indirect immunofluorescence (IF). Antibody was found to be highly prevalent in large mammals in the Orders Artiodactyla and Perissodactyla such as giraffe, Giraffa camelopardalis (3/3 positive), rhinoceros, Ceratotherium simium and Diceros bicornis (7/13), eland, Taurotragus oryx (59/127), buffalo, Syncerus caffer (56/287), kudu, Tragelaphus strepsiceros (17/78), and zebra, Equus burchelli (16/93). In small mammals antibody was found in the sera of 40/293 hares, 22/1,305 rodents, and 1/74 wild carnivores, but not in 522 primates, 176 insectivores, or 19 hyrax. Antibody was also found in the sera of 118/1,978 domestic dogs. The species of wild mammal in which antibody was distributed (with highest antibody prevalence in hares and large herbivores) reflects the feeding preference of immature and adult ticks of the genus Hyalomma, suggesting that Hyalomma sp. are the principal CCHF vectors in the wild.

Animals↗
PubMed1997

Plague in a complex of white-tailed prairie dogs and associated small mammals in Wyoming.

Fleas were collected from white-tailed prairie dogs (Cynomys leucurus) and other small mammals trapped on six grids during a field study near Meeteetse (Wyoming, USA) in 1989 and 1990 to investigate the dynamics of plague in this rodent population. Fleas were identified and tested for Yersinia pestis by mouse inoculation. Yersinia pestis-positive fleas were found on prairie dogs and in their burrows. Flea species on prairie dogs changed from spring to late summer. White-tailed prairie dog numbers were significantly lower in the presence of Y. pestis-positive fleas; however, affected populations generally recovered 1 to 2 yr following absence of detectable plague. Grids where recovery occurred had a high proportion of juvenile male prairie dogs. Eighteen flea species were identified on small mammals, six of which were infected with Y. pestis. Some flea species were associated with a particular small mammal species, while others were found on a broad range of host species. Flea species most important in the potential interchange of Y. pestis between associated small mammals and white-tailed prairie dogs were Oropsylla tuberculata cynomuris, Oropsylla idahoensis, and Oropsylla labis. Plague cycled through the white-tailed prairie dog complex in an unpredictable manner. Each summer the complex was a mixture of colonies variously impacted by plague: some were declining, some were unaffected by plague, and others were recovering from plague population declines. These data provide insight into the dynamics of plague in white-tailed prairie dog complexes, but predicting movement of plague is not yet possible and the role of associated mammals in maintenance of plague is not understood.

Animals↗
PubMed2002

Risk of rabies after mammal bites in Thai children.

The data were collected by questionnaire at the Outpatient Department of Chulalongkorn University Hospital, Bangkok Thailand. This study revealed that 52 per cent of children had pet mammals in their home of which 67 per cent were dogs. 23.6 per cent of these children gave at least one history of a mammal bite inside (53.4%) or outside (46.6%) their house. Mammal bites of children could be found at all ages. However, most were in the age group of 10-14 years (42.3%), and 5-9 years (39.7%). The most common site of injury was on the legs (56.6%) and hands (30.7%). 31.7 per cent and 68.3 per cent of the bitten children incurred WHO category II and III potential rabies exposures (moderate and severe). 61.9 per cent had performed wound cleansing on each bite injury site and 34 per cent did not. 72 per cent of the children who had mammal bites received no post-exposure rabies treatment and 85.7 per cent did not make any effort to capture or observe the animal who had bitten them. Only 10.6 per cent observed the animals for 10 days or more. It was concluded that children are at considerable risk of mammal bites and that they are not receiving optimal care in this canine rabies endemic region and that 50 per cent of human rabies cases in Thailand were in children under 15 years of age.

Adolescent↗
PubMed2006

Parasites of carnivorous mammals in Białowieza Primeval Forest.

BACKGROUND: Although the parasitofauna of wild carnivorous mammals in Poland is quite well recognized, there has been only one research carried on this issue so far in Białowieza Forest--the last lowland primeval forest of temperate zone in Europe. MATERIAL AND METHODS: Twelve wild and two domestic species of carnivorous mammals are living in Białowieza Forest. In our work faeces or intestines of all of them except ermine (Mustela erminea) have been examined and parasites or their eggs (or oocysts) recorded. In total 222 faecal probes from 13 species and 11 intestines of weasels have been investigated. RESULTS: All species of examined carnivorous mammals were infected with parasites. The most infected species has occurred red fox Vulpes vulpes (over 70% infected with parasites) meanwhile only about 30% of otters Lutra lutra were infected. We found at least three protozoan species, one trematode, one tapeworm and nine species of nematodes. Except trematode Alaria alata, all of them are reported for the first time from Białowieza Primeval Forest. Oocysts of coccidia have been found in faeces of nine host species, with the highest prevalence (29.4%) in badger. Six species of carnivorous mammals have been occurred infected with trematodes (highest prevalence 42.1% in wolves) and two with tapeworms (Diphyllobothrium latum with the prevalence 2.6% in otter and 31.6% in wolves). All examined host species were infected with nematodes (with prevalence from 14.7% in lynx to 72.7% in red fox). Results of our work should be treated as preliminary researches on the species composition of parasitic fauna invading carnivorous mammals in Białowieza Primeval Forest.

Animals↗
PubMed1991

Innervation of hairs in the facial skin of marsupial mammals.

The innervation of pelage, guard hairs and vibrissae hairs was studied in five species of marsupial mammals by means of electron microscopy for the first time. This study showed that members of different superfamilies in marsupial mammals displayed the same pattern of hair innervation. This also resembled the pattern seen in the placental mammals. All types of hairs had both longitudinal and transverse lanceolate nerve terminals. Pelage hairs did not have any Merkel cells. Guard hairs were very richly innervated and had free nerve endings, lanceolate nerve endings, many Merkel cells with their associated nerve endings and pilo-Ruffini nerve endings. Vibrissae hairs had free nerve endings, Merkel nerve endings and lamellated corpuscles, but pilo-Ruffini nerve endings were not seen in this investigation. Because of the profusion and variety of innervation in guard hairs of the marsupial mammals, these hairs may have a similar function to vibrissae hairs in placental mammals.

Animals↗
PubMed1990

[Small mammals as leptospirosis carriers on waste dumps].

In 1980-1986 the authors examined 2,720 small mammals (17 species) from six dumps of wastes in South-Bohemia serologically for leptospirosis. 397 small mammals from the agglomeration of Ceské Budĕjovice and 1,399 from four characteristic biotops in the valley of the river Vltava in South-Bohemia were investigated for a comparison. In small mammals from the dump of wastes at Ceské Budĕjovice antibodies against L. grippotyphosa were detected in 4.9%, against the serovars from the serogroup Sejroe in 2.6% and against L. icterohaemorrhagiae in 0.1%. In other five dumps of wastes only L. grippotyphosa antibodies were ascertained in small mammals, namely from 1.6% to 6.7%. In the agglomeration of the town Ceské Budejovice small mammals were positive in 4.0%, also for L. grippotyphosa only, in seven localities in the valley of the river Vltava with the same serovar in an average of 2.3%, with sorex-jalna in 0.1%.

Animals↗
PubMed1996

Interspecific differences between small mammals as hosts of immature Dermacentor variabilis (Acari: Ixodidae) and a model for detection of high risk areas of Rocky Mountain spotted fever.

Fourteen species of small mammals were captured from July 1990 through August 1991 in Tennessee, from which 1,217 immature Dermacentor variabilis and 1 Ixodes dentatus were collected. Mammal species were given scores of importance (TS) as hosts to immature D. variabilis based on mean intensity and prevalence. The rice rat ranked the highest, with a TS = 5, followed by the golden mouse TS = 4, white-footed mouse TS = 3, pine vole TS = 2, cotton rat TS = 1, with the Norway rat, house mouse, and short-tailed shrew all having a TS = 0. Assigning a TS allows a quantitative method for differentiating and ranking small mammals as hosts for immature D. variabilis. Relative abundance of a species can also be important in determining D. variabilis populations, even with a low TS. The potential of Rocky Mountain spotted fever (RMSFP) to occur in an area was estimated using the total score of small mammal hosts in an area and multiplying the relative abundance of important host species. The RMSFP of a site, based only upon small mammal species composition and relative abundance of important host species, was an accurate estimate of adult D. variabilis infesting raccoons and opossums at that trap site (P < or = 0.001). A RMSFP of 1.61 is needed to produce an estimated 252 adults per ha (RMSF threshold) at 98% survival of engorged immature ticks (P < 0.001).

Analysis of Variance↗
PubMed1996

[Leptospira antibodies in small mammals in Eastern Slovakia].

During the five years (1991-1995) mostly free living small mammals were examined serologically for the presence of antibodies to leptospira. Serological examinations were used by Kmety and Bakoss (1978). Altogether, 2493 individuals of 22 species were examined, an important part of host material (69.6%) was caught in two lowland areas which are intensively cultivated landscapes (East Slovakian Lowland and Kosická kotlina basin). The remaining material comes from submontane areas with less agricultural activities. Apodemus flavicollis, A. agrarius, Clethrionomys glareolus were the most frequently examined species. Antibodies to leptospira were demonstrated in 123 mammals (i. e. in 5.0% of hosts) of eleven species. The highest percentage of positive hosts were recorded in 1993 (8.8%) and the lowest (2.6%) in 1995, but the examined samples were different in size and structure of host species. In six most dominant species higher values of antibodies to leptospira were detected in Microtus arvalis (9.2%), followed by Apodemus flavicollis (5.6%), A. agrarius (5.4%) and A. microps (4.9%). The lowest values were found in Clethrionomys glareolus (2.5%) and Sorex araneus (2.3%). In examined hosts we found antibodies to six serovars of leptospira. The most frequently observed antibodies were to leptospira of the serovar L. grippotyphosa (63.2%) and leptospira of the serovar L. sejroe (26.4%). We recorded nonsignificant differences between the values of prevalence to antibodies in small mammal communities from lowland and submontane areas, resp. Our results confirmed differences in the leptospira serovar structure in small mammals of Bohemia and Slovakia, they were connected with different historical development of both areas. Comparing our results with previous examinations (about 20 years ago) in small mammals from eastern Slovakia, a decline of positivity and lower number of leptospira serovars were recorded.

Animals↗
PubMed1998

Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat.

Neurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals.

Acoustic Stimulation↗
PubMed2026

On the origin of animals and placental mammals: a critique of literalist readings of the fossil record.

The fossil record is incomplete, as evidenced by the pervasive presence of ghost lineages throughout the Tree of Life. For example, across placental mammals, at least 720&#x2005;Myr of basal lineages are ghost lineages, that is, lineages that have left no fossil evidence of their past history. In contrast, some studies have suggested that the fossil record is a faithful temporal archive of evolutionary history and thus the times of diversification of clades must be close to the ages of their oldest fossils. Such literalist interpretations have been contradicted by analysis of molecular datasets which, in many cases, indicate that groups including placental mammals and animals may have originated at times substantially older than their fossil records. Some of those studies have further argued that, in the case of animals and placental mammals, molecular clocks are uninformative, suffer from characteristic pathologies, and thus cannot distinguish between recent and ancient hypotheses of diversification. Here, we reexamine these two cases and show, using Bayesian model selection theory, that the explosive diversification models previously proposed for animals and placental mammals have a posterior probability of &#x223c;0. We show the characteristic pathologies purportedly discovered do not exist, highlight errors in previous analyses, and provide advice on best practice for molecular-clock dating analysis.

Animals↗
PubMed2004

Herbicide safety relative to common targets in plants and mammals.

Most modern herbicides have low mammalian toxicity. One of the reasons for this safety is that the target site for the herbicides is not often present in mammals. There are approximately 20 mechanisms of action that have been elucidated for herbicides. Of these, some do share common target sites with mammals. The mechanisms include formation of free radicals, protoporphyrinogen oxidase (PROTOX), glutamine synthetase (GS) and 4-hydroxyphenylpyruvate dioxygenase (HPPD). PROTOX, HPPD and GS inhibitors have been shown to inhibit these enzymes in both plants and mammals and there are measurable effects in mammalian systems. However, the consequences of inhibiting a common target site in plants can be quite different than in animals. What may be a lethal event in plants, eg inhibition of HPPD, can have a beneficial effect in mammals, eg treatment for tyrosinemia type I. These chemicals also have low mammalian toxicity due to rapid metabolism and/or excretion of the herbicide from mammalian systems.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed1999

The evolution of the scrotum and testicular descent in mammals: a phylogenetic view.

The adaptive significance of the scrotum and the evolution of the descent of the testicles and epididymis have been a focus of interest among biologists for a long time. In this paper we use three anatomical character states of the scrotum and descensus: (1) testicles descended and scrotal; (2) testicles descended but ascrotal; (3) testicles not descended (testicondy). These states are then mapped on an up to date phylogeny of the Mammalia. Three main points arise out of this mapping procedure: (1) the presence of a scrotum is either primitive in extant Mammalia or primitive within eutherian mammals except Insectivora; (2) evolution has generally proceeded from a scrotal condition to progressively more ascrotal; (3) loss of testicular descensus is less common in mammalian evolution than is loss of the scrotum. In the light of these findings we discuss some current hypotheses regarding the origin and evolution of the scrotum. We find that these are all incomplete in so far as it is not the presence of the scrotum in various mammal groups that requires explaining. Instead, it is the reverse process, why the scrotum has been lost in so many groups, that should be explained. We suggest that the scrotum may have evolved before the origin of mammals, in concert with the evolution of endothermy in the mammalian lineage, and that the scrotum has been lost in many groups because descensus in many respects is a costly process that will be lost in mammal lineages as soon as an alternative solution to the problem of the temperature sensitivity of spermatogenesis is available.

Animals↗
PubMed1993

Chemical threat to birds and mammals in The Netherlands.

This article reviews the impact of xenobiotic substances on wild birds and mammals in The Netherlands, as recorded in the field over the past 25 yr. First, a brief survey is given of population trends during this period, using a few illustrative examples to indicate the role played by "environmental policy themes" other than diffusion. The present review of the policy theme diffusion is not intended to be exhaustive, but to provide a broad summary of the nature of the problems involved. Based on this review, conclusions are drawn about the ecological compatibility of various groups of xenobiotics with respect to birds and mammals. Because policy-makers are interested in the relative significance of both the various groups of substances and the various environmental themes for the decline of bird and mammal populations in The Netherlands, a provisional estimate of these contributions is also presented. The main conclusion is that, in the context of the policy theme diffusion, PCBs and pesticides have the greatest impact on birds and mammals. PCBs have an impact up to the species level, whereas the main impact of pesticides today is probably ecological, that is, foraging and habitat changes. It is also concluded that the share of the theme diffusion in the sum total of negative environmental influences is approximately one-quarter.

Animals↗
PubMed1975

Cell number and cell density in the cerebellar cortex of man and some other mammals.

The number of cells per unit volume was determined in the cerebellar cortex of man and 19 other mammals. The cell density (i.e. the number of cells per unit volume) decreases from mammals with a low brain weight to those with a higher brain weight. This decrease in the number of cells is found to be proportional for all three layers of the cerebellar cortex. In addition, the ratio of Purkinje cells to granule cells was determined. In contrast to the decrease of all cell types with increasing brain weight, this ratio varies remarkably among the mammals and is not correlated with brain weight. In man, this ratio is 1:2991, while it is lower in all other mammals investigated. These differences in the ratio of Purkinje cells to granule cells and the decrease in cell density with increasing brain weight are discussed in relation to brain evolution.

Animals↗
PubMed1978

The pterygoid and ectopterygoid in mammals.

A dorsal pterygoid element and a ventral ectopterygoid element can be recognised during the development of monotremes, marsupials and eutherian mammals. Their homology with the elements so named in fossils ancestral to mammals can be established by positional evidence. In monotremes the elements remain distinct and show specialised features, including a hamular cartilage in the ectopterygoid of one specimen of Ornithorhynchus. In most higher mammals the pterygoid element is much reduced and is replaced anteriorly by the perpendicular plate of the palatine. Posteriorly the pterygoid element fuses with the ectopterygoid, in many cases before the onset of ossification. The hamular cartilage arises by chondrification within the ectopterygoid element and shows no sign of being a separate morphological entity, but must be regarded as a specialised feature associated with the architecture of the palatal musculature. There is a strong case for the value of recognising that the 'pterygoid process' of higher mammals includes both a pterygoid and an ectopterygoid moiety.

Animals↗