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PubMed2005

Genetic divergence of Campylobacter fetus strains of mammal and reptile origins.

Campylobacter fetus is a gram-negative bacterial pathogen of both humans and animals. Two subspecies have been identified, Campylobacter fetus subsp. fetus and Campylobacter fetus subsp. venerealis, and there are two serotypes, A and B. To further investigate the genetic diversity among C. fetus strains of different origins, subspecies, and serotypes, we performed multiple genetic analyses by utilizing random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and DNA-DNA hybridization. All 10 primers used for the RAPD analyses can distinguish C. fetus strains of reptile and mammal origin, five can differentiate between C. fetus subsp. fetus and C. fetus subsp. venerealis strains, and four showed differences between type A and type B isolates from mammals. PFGE with SmaI and SalI digestion showed varied genome patterns among different C. fetus strains, but for mammalian C. fetus isolates, genome size was well conserved (mean, 1.52 +/- 0.06 Mb for SmaI and 1.52 +/- 0.05 Mb for SalI). DNA-DNA hybridization demonstrated substantial genomic-homology differences between strains of mammal and reptile origin. In total, these data suggest that C. fetus subsp fetus strains of reptile and mammal origin have genetic divergence more extensive than that between the two subspecies and that between the type A and type B strains. Combining these studies with sequence data, we conclude that there has been substantial genetic divergence between Campylobacter fetus of reptile and mammal origin. Diagnostic tools have been developed to differentiate among C. fetus isolates for taxonomic and epidemiologic uses.

Animals↗
PubMed2000

Ventilatory responses to changes in temperature in mammals and other vertebrates.

This article reviews the relationship between pulmonary ventilation (VE) and metabolic rate (oxygen consumption) during changes in ambient temperature. The main focus is on mammals, although for comparative purposes the VE responses of ectothermic vertebrates are also discussed. First, the effects of temperature on pulmonary mechanics, chemoreceptors, and airway receptors are summarized. Then we review the main VE responses to cold and warm stimuli and their interaction with exercise, hypoxia, or hypercapnia. In these cases, mammals attempt to maintain both oxygenation and body temperature, although conflicts can arise because of the respiratory heat loss associated with the increase in ventilation. Finally, we consider the VE responses of mammals when body temperature changes, as during torpor, fever, sleep, and hypothermia. In ectotherms, during changes in temperature, VE control becomes part of a general strategy to maintain constant relative alkalinity and ensure a constancy of pH-dependent protein functions (alphastat regulation). In mammals on the other hand, VE control is aimed to balance metabolic needs with homeothermy. Therefore, alphastat regulation in mammals seems to have a low priority, and it may be adopted only in exceptional cases.

Animals↗
PubMed1985

What transport adaptations enable mammals to absorb sugars and amino acids faster than reptiles?

What digestive adaptations enable mammals to process much more food in much less time with equal or higher digestive efficiency than reptiles and thus to sustain much higher metabolic rates? To answer this question, we measured glucose and proline uptake in small intestinal sleeves of three mammal and three reptile species of similar body size and natural diet. All species exhibit saturable, stereospecific uptake of D-glucose and Na+-dependent L-proline uptake. Passive permeability to glucose is high in hamsters and low in the other species. Uptake increases with temperature up to a maximum around 45-50 degrees C. This temperature dependence may help explain why reptiles bask after meals and why their digestion is impaired if basking is prevented. The total uptake capacity of the small intestine for glucose and proline is seven times higher in mammals than similar-sized reptiles, mainly because the area of mammalian intestine is 4-5.5 times greater. Minor reasons for the higher uptake capacity of mammals are that the transport activity of mammal intestine normalized to quantity of tissue is up to twofold higher and that reptile intestine operates at a lower temperature at night. Vmax for glucose transport varies 10-fold among species, but apparent differences in Km values may be unstirred-layer artifacts. Carrier-mediated uptake of glucose and proline is measurable in the colon of at least three species, but the uptake capacity of the colon is less than 10% of that of the small intestine. An appendix presents a method for measuring the microscopic area of intestines with ridges rather than villi, applies this method to desert iguana intestine, and measures area amplification due to villi in wood rat intestine.

Amino Acids↗
PubMed1985

Mammals: an allometric study of metabolism at tissue and mitochondrial level.

Body composition, mitochondrial volume density, and mitochondrial membrane surface area were measured in six species of mammals representing a 100-fold weight range (18-2,067 g). The mammals examined included three eutherian species, two marsupial, and one monotreme species. The tissues examined were liver, kidney, brain, lung, heart, and skeletal muscle (gastrocnemius). Allometric equations were derived for tissue weight, and the allometric exponents ranged from 0.69 (brain) to 1.01 (skeletal muscle). Allometric relationships for mitochondrial membrane surface area were also determined both per milliliter tissue and per total tissue. Small mammals had a higher mitochondrial membrane surface area per milliliter tissue than large mammals in all tissues examined. These differences were significant in liver, kidney, brain, and heart. Total mitochondrial membrane surface area per tissue had allometric exponents ranging from 0.55 (kidney) to 0.78 (skeletal muscle). When total mitochondrial membrane surface area was summated for the major internal organs examined (liver, kidney, heart, and brain), the allometric equation was mitochondrial membrane surface area (m2) = 3.04 body wt0.59 (g). This was similar to the exponent of standard metabolic rate against body weight in the species examined (i.e., 0.62). The inclusion of skeletal muscle and lung into the summated mitochondrial membrane surface area increased the exponent to 0.76. This is compared with the relationship between maximal O2 consumption and body size in mammals.

Animals↗
PubMed2003

Expression studies of the PIS-regulated genes suggest different mechanisms of sex determination within mammals.

In mammals, the Y-located SRY gene is known to induce testis formation from the indifferent gonad. A related gene, SOX9, also plays a critical role in testis differentiation in mammals, in birds and reptiles. It is now assumed that SRY acts upstream of SOX9 in the sex determination cascade, but the regulatory link which should exist between these two genes remains unknown. Studies on XX sex reversal in polled goats (PIS mutation: Polled Intersex Syndrome) have led to the discovery of a female-specific locus crucial for ovarian differentiation. This genomic region is composed of at least two genes, FOXL2 and PISRT1, which share a common transcriptional regulatory region, PIS. In this review, we present the expression pattern of these PIS-regulated genes in mice. The FOXL2 expression profile of mice is similar to that described in goats in accordance with a conserved role of this ovarian differentiating gene in mammals. On the contrary, the PISRT1 expression profile is different between mice and goats, suggesting different mechanisms of the primary switch in the testis determination process within mammals. A model based on two different modes of SOX9 regulation in mice and other mammals is proposed in order to integrate our results into the current scheme of gonad differentiation.

Animals↗
PubMed2005

Hind limb proportions and kinematics: are small primates different from other small mammals?

Similar in body size, locomotor behaviour and morphology to the last common ancestor of Primates, living small quadrupedal primates provide a convenient model for investigating the evolution of primate locomotion. In this study, the hind limb kinematics of quadrupedal walking in mouse lemurs, brown lemurs, cotton-top tamarins and squirrel monkeys are analysed using cineradiography. The scaling of hind limb length to body size and the intralimb proportions of the three-segmented hind limb are taken into consideration when kinematic similarities and differences are discussed. Hind limb kinematics of arboreal quadrupedal primates, ranging in size between 100 g and 3000 g, are size independent and resemble the hind limb kinematics of small non-cursorial mammals. A common feature seen in smaller mammals, in general, is the horizontal position of the thigh at touchdown and of the lower leg at lift-off. Thus, the maximum bone length is immediately transferred into the step length. The vertical position of the leg at the beginning of a step cycle and of the thigh at lift-off contributes the same distance to pivot height. Step length and pivot height increase proportionally with hind limb length, because intralimb proportions of the hind limb remain fairly constant. Therefore, the strong positive allometric scaling of the hind limb in arboreal quadrupedal primates affects neither the kinematics of hind limb segments nor the total angular excursion of the limb. The angular excursion of the hind limb in quadrupedal primates is equal to that of other non-cursorial mammals. Hence, hind limb excursion in larger cercopithecine primates differs from that of other large mammals due to the decreasing angular excursion as part of convergent cursorial adaptations in several phylogenetic lineages of mammals. Typical members of those phylogenetic groups are traditionally used in comparison with typical primates, and therefore the ;uniqueness' of primate locomotor characteristics is often overrated.

Age Factors↗
PubMed2002

Local hunting and the conservation of large mammals in India.

Hunting by local communities is among the most widespread threats to Indian wildlife, yet, the understanding of its nature, extent, and impacts on wildlife has been poor. We surveyed 2 protected areas--Kudremukha and Nagara-holé--in southern India to assess the impacts of local hunting on large mammals. Detailed interviews with retired and active hunters were employed to describe hunting patterns. Impacts of hunting were assessed by comparing large-mammal abundance in adjacent sites differing in their vulnerability to hunting. In Kudremukha, at least 26 species of mammals were hunted, mostly with guns, at an estimated intensity of 216 hunter-days per month per village. In Nagaraholé, 6 of the 9 focal species of large mammals occurred at significantly lower densities at the heavily hunted site where enforcement capabilities were poorer. Our data underscore the importance of preservationist programs in the conservation of large mammals in a context of extensive local hunting.

Animals↗
PubMed1976

Failure to prove arenavirus infection among the small mammals from an endemic area of Korean hemorrhagic nephrosonephritis.

In the light of recent knowledge on a complex of diseases caused by a new group of viruses, arenaviruses, virological studies largely directed toward small field mammals were undertaken during 1973-1974 aiming at etiological clarification of Korean hemorrhagic nephrosonephritis (KHNN). Specimens were collected in an endemic area of KHNN located north to northeast of Seoul. Virus isolation tests with 299 urine specimens and 131 mite pools recovered from small mammals and 14 acute stage sera from typical cases yielded negative results. Complement-fixation (CF) tests failed to detect antibodies against the antigens of Congo, lymphocytic choriomeningitis (LCM), Tacaribe, and Pichinde viruses among 366 small mammal sera. In addition, CF tests of 59 of the above sera against Apoi and Lassa virus antigens were negative. The results do not support the likelihood of an arenavirus being transmitted among Korean small field mammals, the overwhelming majority of which were Apodemus agrarius. A hypothesis that KHNN is caused by a virus of small field mammal origin was not proved within the technical limit of relatively unsophisticated methods employed herein.

Adolescent↗
PubMed1999

Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes, and cancer.

Mammals have seven cervical vertebrae, a number that remains remarkably constant. I propose that the lack of variation is caused by developmental constraints: to wit, changes in Hox gene expression, which lead to changes in the number of cervical vertebrae, are associated with neural problems and with an increased susceptibility to early childhood cancer and stillbirths. In vertebrates, Hox genes are involved in the development of the skeletal axis and the nervous system, among other things. In humans and mice, Hox genes have been shown also to be involved in the normal and abnormal (cancer) proliferation of cell lines; several types of cancer in young children are associated with abnormalities in Hox gene expression and congenital anomalies. In these embryonal cancers the incidence of a cervical rib (a rib on the seventh cervical vertebra, a homeotic transformation of a cervical vertebra towards a thoracic-type vertebra) appears to be increased. The minimal estimate of the selection coefficient acting against these mutations is about 12%. In birds and reptiles variations in the number of cervical vertebrae have frequently occurred and there is often intraspecific variability. A review of the veterinary literature shows that cancer rates appear lower in birds and reptiles than in mammals. The low susceptibility to cancer in these classes probably prevents the deleterious pleiotropic effect of neonatal cancer when changes in cervical vertebral number occur. In mammals there is, thus, a coupling between the development of the axial skeleton and other functions (including the proliferations of cell lines). The coupling of functions is either a conserved trait that is also present in reptiles and birds, but without apparent deleterious effects, or the coupling is new to mammals due to a change in the functioning of Hox genes. The cost of the coupling of functions in mammals appears to be an increased risk for neural problems, neonatal cancer, stillbirths, and a constraint on the variability of cervical vertebral number.

Animals↗
PubMedDate not supplied

[Life-history variation within a taxon: a comparative analysis of birds and mammals].

Most studies on life-history evolution discuss the necessity of distinguishing between extrinsic and intrinsic sources of variability in life-history traits. I use log/log plots of yearly neonate production in daugters (b) versus adult mortality (Ma) for 75 bird species and 88 mammal species to compare graphically life-history "fields" arranged by these selective forces along a "slow-fast continuum". Under the assumptions of steady-state and linear relationship between adult mortality and reproductive effort, as well as between juvenile survival and relative neonate weight, it is possible to place additional axes in the two-dimentional plot, and to predict covariations among demographic and individual growth traits. The functional regression analysis shows, that the assumptions are completely fulfilled, at least for birds, but mammals show nonlinear relationship between adult mortality and reproductive effort. This can be explained by peculiarities of metabolism and parental care in small mammals with high reproductive output. Hence, for birds the axis of relative neonate weight approximately coincides in direction with the juvenile survivorship axis, but this is not a case for mammals. In both taxa, the relative neonate weight is an invariant in relation to fecundity and adult mortality (but not in relation to adult body weight). This important feature, together with other intrinsic (energetic and phylogenetic) constraints, explains well-documented close covariations among traits, even when the effect of body size is factored out. It is argued that life-history and body size variations in birds and mammals mainly depend on a pattern of temporal resource deficiency, although this impact cannot be separated from that of extrinsic juvenile mortality.

Animals↗
PubMed2003

Provision of tricuspid valve leaflets by septal papillary muscles in the right ventricle of human and other mammal hearts.

Leaflets of the tricuspid valve are provided by tendinous cords extending from the papillary muscles. The situation is complicated with the septal muscles, which generally occur in two groups, one as constant musculus coni arteriosi and the second as other variable septal muscles. We tested whether there is a variability in the provision of the tricuspid valve in different taxonomical groups of mammals. The material examined consisted of 299 hearts of mammals (Primates, Ungulata, Carnivora, Lagomorpha, Rodentia, Marsupialia). The musculus coni arteriosi in the majority of mammals provided only the front leaflet, but among Ungulata and Rodentia it provided simultaneously the front and septal leaflet. The other septal muscles provided the front, septal and even back leaflets. The following regularity was observed: in the hearts of Primates provision of the front leaflet and the front part of the septal leaflet predominated, among Ungulata the muscles provided the middle part of the septal leaflet, but among the other mammals the rest of the septal muscles provided, significantly, the back part of the septal leaflet. Such a provision was characteristic for predators, hares, rodents and marsupials. These circumstances may allow the conclusion to be drawn that there is a taxonomical dependence in the provision of the tricuspid valve in the hearts of the mammals under examination.

Animals↗
PubMed2003

Feeding success of Lutzomyia evansi (Diptera: Psychodidae) experimentally exposed to small mammal hosts in an endemic focus of Leishmania chagasi in northern Colombia.

Lutzomyia evansi is the vector of Leishmania chagasi in northern Colombia. Differences in feeding success were revealed, when this phlebotomine sand fly was fed on five species of small mammal hosts from an endemic focus of visceral leishmaniasis. In each trial, 50 female sand flies were provided access to similar-sized depilated areas of the hind foot of each of 44 individual mammals and allowed to feed for 30 minutes. The number of engorged sand flies was counted at the end of each trial and compared among host species by analysis of variance and Tukey's multiple comparisons test. Sand flies fed least successfully on Sciurus granatensis, a common squirrel in the endemic area. It has not been found infected with L. chagasi. Intermediate numbers of sand flies engorged on Heteromys anomalus and Zygodontomys brevicauda, but these two mammals have not been found infected with L. chagasi and are not expected to be important in transmission. Sand flies fed most successfully on Didelphis marsupialis and Proechimys canicollis. These are the two most abundant mammals in the endemic area and frequently are infected. Results provided further evidence that these two species are the wild mammals with the greatest impact on transmission of L. chagasi in northern Colombia.

Animals↗
PubMedDate not supplied

Influenza virus infections in mammals.

The natural reservoir of all known subtypes of influenza A viruses are aquatic birds, mainly of the orders Anseriformes and Charadriiformes in which the infection is asymptomatic and the viruses stay at an evolutionary equilibrium. However, mammals may occasionally contract influenza A virus infections from this pool. This article summarizes: (i) natural infections in mammals including pigs, horses, marine mammals, ferrets, minks; (ii) results from experimental infections in several animal models including mice, ferrets, primates, rats, minks, hamsters and (iii) evidence for the increased pathogenicity of the current influenza A H5N1/Asia viruses for mammals. Several reports have shown that a number of mammalian species, including pigs, cats, ferrets, minks, whales, seals and finally also man are susceptible to natural infection with influenza A viruses of purely avian genetic make up. Among the mammalian species naturally susceptible to avian influenza virus the pig and the cat might exert the greatest potential public health impact. Despite numerous studies in animal and cell culture models, the basis of the extended host spectrum and the unusual pathogenicity of the influenza A H5N1 viruses for mammals is only beginning to be unraveled. Recently, also the transmission of equine influenza A virus to greyhound racing dogs has been documented.

Animals↗
PubMed1996

The occurrence of antibodies to Naegleria species in wild mammals.

Individuals from 13 wild mammalian species collected in southwestern Tennessee were serologically positive for anti-Naegleria spp. antibodies (ANA). This is the first report of ANA in wild mammals. Interspecific differences in the occurrence of ANA and titers indicate that wild mammals have differing degrees of contact with Naegleria spp. based on ecological or behavioral adaptations, and possibly the innate ability of a species to produce ANA. Intraspecifically, it appears that if a mammal is exposed to Naegleria spp. in the environment, titers of ANA will not significantly differ, regardless of age or sex. Adults of many species had significantly higher occurrences of ANA. Populations of juvenile wild mammals are probably at higher risk than adults to naeglerial infection in the environment, not because of lower titers, but because their chance of having ANA is less than adults. Differences in the occurrence of ANA in wild mammals may also reflect how humans are exposed to Naegleria spp. in the environment.

Amebiasis↗
PubMed1992

The mechanism of suckling in two species of infant mammal: miniature pigs and long-tailed macaques.

Suckling is the form of feeding unique to infant mammals. The mechanism used by infant mammals to withdraw liquid from the nipple is the subject of considerable debate. Suckling has been examined in two species of infant mammals: miniature pigs and long-tailed macaques. In both species radio-opaque markers were inserted into the tongue and jaws; the movements of the jaw and tongue (and also of specific regions within the tongue) plus the movement of milk containing barium were studied by high-speed cineradiography (100 and 150 frames/sec). In the case of macaques, simultaneous pressure transducer recordings were also made. In both species, liquid moved out of the nipple as the intraoral space was expanded by a combination of tongue movement (negative pressure pumping) coupled with jaw opening. There was no evidence for expression (positive pressure on the nipple) in either species, strongly supporting the view that a suction mechanism is responsible for acquisition of milk from the nipple. Subsequent intraoral transport was different in the two species. The pigs used a second pump mechanism at the base of the tongue to transport liquid through the pillars of the fauces into the valleculae. The monkeys used a "squeeze-back" mechanism similar to the transport mechanism documented for adult macaques. Further work with other species can test our tentative hypothesis that all mammals use a negative pressure suction for acquisition, but, as is true for adult mammals, infants may use different transport mechanisms to form and move the bolus.

Animals↗
PubMed1998

Radiation exposure and dose to small mammals in radon-rich soils.

Protection of the environment from radionuclide releases requires knowledge of the normal background levels of radiation exposure in the exposed biotic community and an estimate of the detriment caused by additional exposure. This study modeled the background exposure and dose to the lungs of small burrowing mammals from 222Rn in artificial burrows in radon-rich soils at a site in southeastern Manitoba. E-PERM chambers used to measure 222Rn in soil showed good reproducibility of measurement, with an average coefficient of variance (CV) of about 10%. Geometric mean (GM) 222Rn concentrations at nine randomly selected sites ranged from 5,490 Bq/m3 (GSD = 1.57, n = 7) to 41,000 Bq/m3 (GSD = 1.02, n = 5). Long-term monitoring of 222Rn concentrations in artificial burrows showed large variation within and between burrows and did not show consistent variation with season, orientation of the burrow opening, or levels of 226Ra in the soil. Annual GM concentrations in individual burrows ranged from 7,480 Bq/m3 (GSD = 1.60) to 18,930 Bq/m3 (GSD = 1.81) in burrows several meters apart. A grand GM of 9,990 Bq/m3 (GSD = 1.81, n = 214) was measured over the site for the year. An exposure model was constructed for five small mammal species based on their respiration rates and the number of hours spent in the burrow, active or hibernating, exposed to soil gas 222Rn, and the time spent out of the burrow exposed to atmospheric 222Rn. A background dose of 0.9 mGy/a from atmospheric 222Rn (40 Bq/m3) was estimated for a large-bodied (80 kg), nonburrowing animal living on the soil surface. The highest exposures (mJ/a) in burrowing mammals occurred in those species with the highest respiration rates. Hibernation accounted for a small fraction of total annual exposure (<5%) because of very low respiration rates during this period. Absorbed dose to lung (mGy/a) was highest in the pocket gopher and decreased in the larger animals because of larger lung mass. Using mean 222Rn concentrations from the field studies and an equilibrium factor (F) of 0.5, doses to lung ranged from 90 mGy/a in the badger to 700 mGy/a in the pocket gopher. These doses closely correspond to those estimated from published dose conversion factors (DCFs) of 1.4 mGy per mJ . h/m3 for whole lung. For the ground squirrel, the DCF approach gives an estimated dose of 300 mGy/a versus 270 using the respiratory flow rate method. Based on these results, doses exceeding 500 mGy/a may be common in mammals and birds (i.e. the burrowing owl) living in radon-rich soils. Published risk coefficients for small mammals suggest that about 17 cancers would occur in 1,000 animals at these exposure rates. Although the potential effects from these exposures were not examined in this study, the study raises questions about how the animals may respond physiologically to this largely natural stress.

Animals↗
PubMed1987

Selenium accumulation in mammals exposed to contaminated California irrigation drainwater.

In May 1984, 332 mammals of 10 species were collected at Kesterson Reservoir (San Joaquin Valley, Merced Co., CA), which had received selenium-laden irrigation drainwater, and at the nearby Volta Wildlife Area, which had not. The study concentrated on the California vole (Microtus californicus); 88 were taken at Kesterson, 89 at Volta. Mean selenium concentrations in livers were as much as 522 times higher at Kesterson. There were species-to-species differences at Kesterson; higher selenium concentrations occurred in carnivorous species and/or species that feed on foods closely linked to pond water. There were also pond-to-pond differences at Kesterson; drainwater historically was delivered to Ponds 1 and 2, where concentrations in 1984 were higher, with subsequent flow to other ponds, where they were lower. Whereas none of 50 adult female voles from Kesterson was pregnant, 12 of 41 (29%) from Volta were pregnant. However, this cessation of reproductive activity at Kesterson was probably not due to selenium toxicity but could have resulted because drying conditions at Kesterson forced voles to a seed diet earlier than at Volta. One malformation was found among five embryonic litters of three species from Kesterson. Mammals seem much less susceptible to selenium-induced embryonic abnormalities than birds. No adverse impacts of selenium on wild mammals were demonstrated; however, some sensitive species might have been extirpated from Kesterson before this study began. In addition, high concentrations in small mammal species at Kesterson may threaten predatory birds and mammals that feed on them, with the endangered San Joaquin kit fox (Vulpes macrotis mutica) of particular concern.

Abnormalities, Drug-Induced↗
PubMed1995

Trace element concentrations in cetacean liver tissues archived in the National Marine Mammal Tissue Bank.

The National Biomonitoring Specimen Bank (NBSB), a collaborative project of several U.S. government agencies, includes marine mammal tissues collected for the Alaska Marine Mammal Tissue Archival Project (AMMTAP) and the National Marine Mammal Tissue Bank (NMMTB). Tissues were collected from 139 animals representing 13 species of marine mammals from around the U.S. Recently, concentrations for up to 30 elements in liver tissues of nine long-finned pilot whales (Globicephala melas), six harbor porpoises (Phocoena phocoena), and four white-sided dolphins (Lagenorhynchus acutus) from the NMMTB were measured using instrumental neutron activation analysis. Results from analyses of these tissues are presented, compared with results for liver tissues from other marine mammals from the AMMTAP, and compared with published values.

Animals↗