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At least 1,099 records · Page 61Linked to original sources
PubMed2006

The origin and early radiation of the therapsid mammal-like reptiles: a palaeobiological hypothesis.

The replacement of the basal synapsid pelycosaurs by the more 'mammal-like' therapsids in the Permian was an important event in the history of tetrapods because it initiated the eventual transition to the mammals. It is also an example of taxon replacement in the fossil record that is unusually amenable to explanation, based on a combination of analysis of the biological significance of the inferred character changes, with the stratigraphic, palaeogeographic and palaeoecological circumstances of the time. An hypothesis is presented in which the origin of the therapsids resulted from a correlated progression of character evolution leading to higher levels of metabolic activity and homeostatic regulation of the body. It was a response to the availability of a seasonally arid, savanna-like biome. The subsequent explosive radiation of therapsids was associated with habitat expansion made possible by the Mid-Permian development of geographical continuity between that biome and the temperate biomes. The final extinction of the pelycosaurs was a case of incumbent replacement by the new therapsid lineages.

Animals↗
PubMed2006

Ultrastructural analysis of the integument of a desert-adapted mammal, the one-humped camel (Camelus dromedarius).

In this study, we conducted a light microscopic and ultrastructural analysis of the integument of the one-humped camel (Camelus dromedarius). In general, the epidermal strata of the camel integument appeared typical of those found in non-desert mammals. Two cell populations were noted in the stratum basale: one with a flat, non-serrated base and the other with a highly serrated base. Typical fine structure was observed in keratinocytes of the stratum spinosum and stratum granulosum. The stratum corneum was six to 10 cells thick. Within the different strata, overall cell morphologies and the general distribution and relative abundance of cellular organelles appeared typical. Dermal features included the presence of myoepithelial cells surrounding apocrine tubular glands. Inter- or intracellular canaliculi within the secretory cells of the apocrine glands, reported to be present in certain other non-desert mammals, were not evident in the camel. Together, these data indicate that while the camel is clearly adapted for a desert lifestyle, these adaptations do not include significant specializations at the cellular or subcellular level in the integument.

Adaptation, Physiological↗
PubMed2005

Morbillivirus infections in aquatic mammals: a brief overview.

Since 1987, at least eight morbillivirus infection (MI) epidemics have caused mass mortality of several free-living pinniped and cetacean populations around the world. The responsible agents, all belonging to the genus Morbillivirus (family Paramyxoviridae), have been characterized as either "canine distemper virus" strains, infecting pinnipeds, or as three new morbilliviruses, namely "phocid (phocine) distemper virus" , "porpoise morbillivirus" and "dolphin morbillivirus" . The last two agents are currently gathered under the common denomination of "cetacean morbillivirus". At post-mortem examination, a commonly occurring macroscopic lesion is represented by more or less severe bilateral pneumonia, with consolidation, congestion and oedema of both lungs, which fail to collapse. Histologically, a non-suppurative broncho-interstitial pneumonia, characterized by type II pneumocyte hyperplasia and by formation of endobronchial, endobronchiolar and endoalveolar "Warthin-Finkeldey type" syncytia, as well as a multifocal, non-suppurative encephalitis, associated with a severe and generalized lymphoid tissue depletion, are common pathological findings. Furthermore, eosinophilic viral inclusions are often detected, at both the intracytoplasmic and intranuclear level, within bronchial and bronchiolar epithelial, pulmonary syncytial, neuronal and other cell types. These inclusions, along with lymphoid and other cellular elements, are often found to be immunohistochemically positive for morbillivirus antigen. Among the still debated, or even controversial issues regarding MI in sea mammals, the one related to the origin of their causative agents is of particular concern. Another intriguing issue regards the synergistic effects, if any, associated with chronic exposure to a number of environmental pollutants, such as organochlorines and heavy metals. In fact, it is also unknown whether and how these chemicals contribute towards modulating the pathogenic and pathogenetic activity primarily displayed by sea mammal morbilliviruses.

Animals↗
PubMed2006

Evidence of solitary chemosensory cells in a large mammal: the diffuse chemosensory system in Bos taurus airways.

The diffuse chemosensory system (DCS) of the respiratory apparatus is composed of solitary chemosensory cells (SCCs) that resemble taste cells but are not organized in end organs. The discovery of the DCS may open up new approaches to respiratory diseases. However, available data on mammalian SCCs have so far been collected from rodents, the airways of which display some differences from those of large mammals. Here we investigated the presence of the DCS and of SCCs in cows and bulls (Bos taurus), in which the airway cytology is similar to that in humans, focusing our attention on detection in the airways of molecules involved in the transduction cascade of taste [i.e. alpha-gustducin and phospholipase C of the beta2 subtype (PLCbeta2)]. The aim of the research was to extend our understanding of airway chemoreceptors and to compare the organization of the DCS in a large mammal with that in rodents. Using immunocytochemistry for alpha-gustducin, the taste buds of the tongue and arytenoid were visualized. In the trachea and bronchi, alpha-gustducin-immunoreactive SCCs were frequently found. Using immunocytochemistry for PLCbeta2, the staining pattern was generally similar to those seen for alpha-gustducin. Immunoblotting confirmed the expression of alpha-gustducin in the tongue and in all the airway regions tested. The study demonstrated the presence of SCCs in cows and bulls, suggesting that DCSs are present in many mammalian species. The description of areas with a high density of SCCs in bovine bronchi seems to indicate that the view of the DCS as made up of isolated cells totally devoid of ancillary elements is probably an oversimplification.

Animals↗
PubMedDate not supplied

Cardiomyoplasty: comparison of latissimus dorsi muscles of three large mammals with that of human.

Cardiomyoplasty has the potential to become an alternative therapy for congestive heart failure patients and is presently in Phase III clinical trials. In experimental studies, it is necessary to use an animal with muscle characteristics that resemble those of humans. Therefore, the purpose of this study was to compare morphological and biochemical characteristics of the latissimus dorsi muscle (LDM) of three common large mammals with those of human. Of the three mammals studied, the goat had the most overall similarities to the human when comparing mitochondrial capacity, percent fiber types, fiber areas, myofibrillar (MF)-AT-Pase activity, and 72-kDa heat shock protein (HSP) content. The pig was dissimilar to the human in its fiber-type arrangement, glycolytic capacity, percent fiber type, MF-ATPase activity, and HSP-72 content. The dog differed from the human in that it had high-mitochondrial enzyme activity, a fiber-type profile consisting of all high-aerobic fibers, and fiber cross-sectional areas that were nearly half those of humans. These findings show that the LDM of the goat most resembles that of the human.

Animals↗
PubMed1991

Tissue osmolality in intestinal villi of four mammals in vivo and in vitro.

Using a freezing point depression method osmolality in the intestinal tissue of four mammals (gerbils, guinea-pigs, rabbits and rats) was estimated in vivo, during fluid transport from an isotonic electrolyte-glucose solution. Net fluid transport was also measured. In gerbils, guinea-pigs and rabbits tissue osmolality was also estimated during in vitro conditions. A marked hyperosmolality was observed in vivo in the upper parts of the villi of all four mammals studied. The tissue osmolality was significantly higher than that seen in the same species during in vitro conditions. A villus hyperosmolality was observed also in species which exhibited a net fluid secretion (guinea-pig, rabbit ileum), indicating that the fluid secretion emanated from the intestinal crypts. Based on the results of the present experiments and on observations made in earlier experiments performed on the cat, it is proposed that the villus hyperosmolality is created by a countercurrent multiplier present in the intestinal villus. The hyperosmolar compartment in the villus tissue creates the force that drives fluid from lumen to tissue.

Animals↗
PubMed1997

Visualizing gene expression in living mammals using a bioluminescent reporter.

Control of gene expression often involves an interwoven set of regulatory processes. As information regarding regulatory pathways may be lost in ex vivo analyses, we used bioluminescence to monitor gene expression in living mammals. Viral promoters fused to firefly luciferase as transgenes in mice allowed external monitoring of gene expression both superficially and in deep tissues. In vivo bioluminescence was detectable using either intensified or cooled charge-coupled device cameras, and could be detected following both topical and systemic delivery of substrate. In vivo control of the promoter from the human immunodeficiency virus was demonstrated. As a model for DNA-based therapies and vaccines, in vivo transfection of a luciferase expression vector (SV-40 promoter and enhancer controlling expression) was detected. We conclude that gene regulation, DNA delivery and expression can now be noninvasively monitored in living mammals using a luciferase reporter. Thus, real-time, noninvasive study of gene expression in living animal models for human development and disease is possible.

Animals↗
PubMed2003

Hypaxial motor patterns and the function of epipubic bones in primitive mammals.

Since the first description of epipubic bones in 1698, their functions and those of the associated abdominal muscles of monotremes and marsupial mammals have remained unresolved. We show that each epipubic bone is part of a kinetic linkage extending from the femur, by way of the pectineus muscle, to the epipubic bone, through the pyramidalis and rectus abdominis muscles on one side of the abdomen, and through the contralateral external and internal oblique muscles to the vertebrae and ribs of the opposite side. This muscle series is activated synchronously as the femur and contralateral forelimb are retracted during the stance phase in locomotion. The epipubic bone acts as a lever that is retracted (depressed) to stiffen the trunk between the diagonal limbs that support the body during each step. This cross-couplet kinetic linkage and the stiffening function of the epipubic bone appear to be the primitive conditions for mammals.

Abdominal Muscles↗
PubMed1965

Organ weights in primates and other mammals.

In mammals the weight of the heart, kidney, lungs, and other organs can be related to total body weight through power laws (allometry). Weights of primate organs are analyzed by this technique. Allometric coefficients and size-independent organ-weight or body-form ratios may be used to compare primates, including humans, and other mammals.

Animals↗
PubMed1995

Gametic imprinting in mammals.

Embryonic development in mammals is distinct from that in other vertebrates because it depends on a small number of imprinted genes that are specially expressed from either the maternal or paternal genome. Why mammals are uniquely dependent on sexual reproduction and how this dependency is dictated at a molecular level are questions that have been intensively investigated during the past 2 years. Gene inactivation experiments have confirmed predictions that imprinted genes regulate embryonic and placental growth and that DNA methylation is part of the imprinting mechanism. Despite these considerable achievements, the reason why imprinted hemizygosity is used as a mechanism to regulate the intrauterine growth of mammalian embryos remains elusive.

Alleles↗
PubMed2000

Sink or swim: strategies for cost-efficient diving by marine mammals.

Locomotor activity by diving marine mammals is accomplished while breath-holding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonged gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged.

Animals↗
PubMed1987

Climbing adaptations in the early eocene mammal Chriacus and the origin of artiodactyla.

A virtually complete articulated skeleton of the arctocyonid Chriacus, recently found in northern Wyoming, is one of the most intact early Eocene mammal skeletons ever found. It exhibits numerous adaptations characteristic of mammals that climb, including strong bony crests and processes (reflecting powerful musculature), ability for considerable forearm supination, a highly mobile ankle joint, plantigrade feet, curved and transversely compressed claws, and a long, possibly semiprehensile tail. These features contrast sharply with those of the oldest artiodactyls and indicate that Chriacus or a similar arctocyonid was not ancestral to the Artiodactyla, as has been proposed.

Adaptation, Physiological↗
PubMed2026

Adaptation across an extreme elevational gradient in Andean leaf-eared mice, the world's highest-dwelling mammal.

Andean leaf-eared mice (Phyllotis vaccarum) live at the highest elevations of any mammal, and they also have the broadest elevational range, from sea level to mountain summits of >6700 meters. Highland populations have evolved an enhanced thermogenic capacity in hypoxia relative to lowland conspecifics, and this improved physiological performance is associated with an increased mitochondrial respiratory capacity in skeletal muscle. Population genomic analyses identified mechanisms of hypoxia adaptation and revealed an unanticipated dimension of environmental adaptation in P. vaccarum because selection on biotransformation pathways suggests an evolved capacity to metabolize plant-derived dietary toxins. The world's highest-dwelling mammal has adapted to habitats at both the low- and high-elevation limits of its range, and much of the elevation-related selection relates to previously unappreciated aspects of feeding ecology.

Animals↗
PubMed2006

Characterization of a Brucella sp. strain as a marine-mammal type despite isolation from a patient with spinal osteomyelitis in New Zealand.

Naturally acquired infection of humans with a marine mammal-associated Brucella sp. has only been reported once previously in a study describing infections of two patients from Peru. We report the isolation and characterization of a strain of Brucella from a New Zealand patient that appears most closely related to strains previously identified from marine mammals. The isolate was preliminarily identified as Brucella suis using conventional bacteriological tests in our laboratory. However, the results profile was not an exact match, and the isolate was forwarded to four international reference laboratories for further identification. The reference laboratories identified the isolate as either B. suis or B. melitensis by traditional bacteriological methods in three laboratories and by a molecular test in the fourth laboratory. Molecular characterization by PCR, PCR-restriction fragment length polymorphism, and DNA sequencing of the bp26 gene; IS711; the omp genes omp25, omp31, omp2a, and omp2b; IRS-PCR fragments I, III, and IV; and five housekeeping gene fragments was conducted to resolve the discrepant identification of the isolate. The isolate was identified to be closely related to a Brucella sp. originating from a United States bottlenose dolphin (Tursiops truncatus) and common seals (Phoca vitulina).

Animals↗
PubMed2001

Monoclonal antibody-based competitive enzyme-linked immunosorbent assay for detection of morbillivirus antibody in marine mammal sera.

A competitive enzyme-linked immunosorbent assay (cELISA), using two monoclonal antibodies (MAbs), was developed and compared with the standard virus neutralization test (VNT) for detecting antibodies against canine distemper virus (CDV) and phocine distemper virus (PDV) in sera from dogs and various species of marine mammals. The test depends on the blocking of MAb binding to solid-phase antigen in the presence of positive serum. Test conditions were optimized by using control VNT-negative and -positive sera specific for CDV and PDV. A positive cutoff value of 30% inhibition, which represents the mean cutoff of a VNT-negative population (n = 623) plus 2 standard deviations, was adopted for the test. A total of 736 serum samples were tested by the new cELISA and by the VNT as the "gold standard." An unexpected but useful finding was the ability of this CDV- and PDV-specific cELISA to also detect antibodies against the related pair dolphin morbillivirus and porpoise morbillivirus. Based on a subpopulation of 625 sera used in statistical analyses, the overall sensitivity and specificity of cELISA relative to those of the VNT were 94.9 and 97.7%, respectively. Because the cELISA proved to be nearly as sensitive and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for suspect CDV or PDV cases and would also be useful for epidemiological surveillance of morbilliviral infections in marine mammal populations.

Animals↗
PubMed1997

Antibodies to Brucella in marine mammals around the coast of England and Wales.

Following the isolation of previously unrecognised species of Brucella from stranded seals and cetaceans in Scotland and northern England, a serological survey was carried out to investigate the range of marine mammal species which may have been exposed to Brucella species around the coasts of England and Wales, the prevalence of infection and the temporal and geographical distribution of seropositive animals. Serum collected from 153 stranded marine mammals from the coasts of England and Wales between 1989 and 1995 were tested by competitive and indirect ELISA. Positive titres were recorded for six of 62 (10 per cent) grey seals (Halichoerus grypus), one of 12 (8 per cent) common seals (Phoca vitulina), 11 of 35 (31 per cent) harbour porpoises (Phocoena phocoena) and nine of 29 (31 per cent) common dolphins (Delphinus delphis) tested. Positive titres were also found in a striped dolphin (Stenella coeruleoalba), a bottlenose dolphin (Tursiops truncatus), a killer whale (Orcinus orca) and a pilot whale (Globicephala melas). The seropositive animals were from all around the coasts of England and Wales and the first seropositive sample was from a common dolphin in 1990.

Animals↗
PubMed1981

Physiology of diving in marine mammals.

Natural dives are usually short and aerobic, involving swimming effort that is not energetically costly. Present evidence indicates few, if any, major biochemical enzyme adaptations that would promote an extended anaerobic capacity in marine mammals. We have discussed the lack of evidence for unusual biochemical adaptations for anaerobiosis and the importance and characteristics of natural aerobic dives. What explanation can we offer for the known capability of some marine mammals, such as Weddell seals and sperm whales, to remain submerged for over an hour? Attributes that serve them well for shorter dives are important also for long dives, such as: (a) a large total oxygen store relative to body size, and (b) parsimonious use of blood oxygen due to the lowered energy requirements of various organs. During long dives, some organs deplete their oxygen stores, become predominately dependent on anaerobic metabolism, and build up large quantities of lactate. The result is a degree of fatigue that leaves the animal incapable of further intense diving activities for some time. Consequently, long anaerobic dives are quite rare in nature.

Animals↗
PubMed2005

Molecular cloning and expression of leptin in gray and harbor seal blubber, bone marrow, and lung and its potential role in marine mammal respiratory physiology.

Leptin is a multifunctional hormone, produced predominantly in adipocytes. It regulates energy balance through its impact on appetite and fat metabolism, and its concentration indicates the size of body fat reserves. Leptin also plays a vital role in stretch-induced surfactant production during alveolar development in the fetus. The structure, expression pattern, and role of leptin have not previously been explored in marine mammals. Phocid seals undergo cyclical changes in body composition as a result of prolonged fasting and intensive foraging bouts and experience rapid, dramatic, and repeated changes in lung volume during diving. Here, we report the tissue-specific expression pattern of leptin in these animals. This is the first demonstration of leptin expression in the lung tissue of a mature mammal, in addition to its expression in the blubber and bone marrow, in common with other animals. We propose a role for leptin in seal pulmonary surfactant production, in addition to its likely role in long-term energy balance. We identify substitutions in the phocine leptin sequence in regions normally highly conserved between widely distinct vertebrate groups, and, using a purified seal leptin antiserum, we confirm the presence of the leptin protein in gray seal lung and serum fractions. Finally, we report the substantial inadequacies of using heterologous antibodies to measure leptin in unextracted gray seal serum.

Adipose Tissue↗