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At least 163 records · Page 9Linked to original sources
PubMed1984

Dimensional analysis and dynamic response characterization of mammalian peripheral vestibular structures.

Extensive morphometric measurements were made on the vestibular system of the rabbit ( Oryctulagus cuniculus), the gerbil (Meriones unguiculatus), the chinchilla (Chinchilla laniger ), and the squirrel monkey (Saimiri sciureus) from serial sections of temporal bones. Additionally, a more limited set of measurements were also completed on the owl monkey (Aotus trivirgatus), the Capuchin monkey (Cebus sp.), the harp seal ( Pagophilus groenlandicus Erxleben , 1777), and the two-toed sloth ( Choloepus sp.). The following measurements were made: 1) radius of curvature (R) of each membranous semicircular canal (herein called semicircular duct-see nomenclature in Nomina Anatomica (1968) ), 2) cross-sectional diameter of the ducts and the osseous semicircular canals, and 3) some pertinent morphometrics of the cristae ampullares and the utricle. In all species studied 1) the radii of curvature of the three semicircular ducts are dissimilar, with that of the lateral duct being as small as, or smaller than, those of the anterior and posterior ducts; 2) R for the anterior duct is largest in the harp seal and the rabbit; 3) the canal and duct dimensions are largest in the Capuchin and squirrel monkeys, the two-toed sloth, and the harp seal, and smallest in the gerbil; 4) the proportion of otic fluid "space" that is occupied by endolymph shows a ranking of gerbil greater than rabbit greater than two-toed sloth greater than chinchilla = owl monkey greater than squirrel monkey greater than Capuchin monkey greater than harp seal; and 5) the gross ampullary and utricular dimensions are largest in the harp seal and smallest in the gerbil. These measurements were used for determining the time constants describing semicircular-canal dynamics in the Steinhausen (1931, 1933) and Oman -Marcus (1980) equations.

Animals↗
PubMed1982

Hosts of sandfly vectors of Leishmania braziliensis guyanensis in the central Amazon of Brazil.

The blood meals of 2,569 phlebotomine sandflies from areas endemic for cutaneous leishmaniasis in the central Amazon of Brazil were tested by the microcapillary precipitin method to determine their vertebrate hosts. The two-toed sloth, Choloepus didactylus, was the predominant host of two incriminated vectors of Leishmania braziliensis guyanensis in the region, Lutzomyia umbratilis and Lu. anduzei (64.0% and 63.6%, respectively). The Lu. "shannoni" group, a complex of several species in which females are indistinguishable, also fed predominantly on sloths (73.0%). Species comprising the Lu. "shannoni" group have not been implicated as vectors of leishmaniasis; however, their feeding patterns in the study area illustrate their potential involvement in the transmission of the parasites to two-toed sloths, which are the principal reservoir hosts of L. braziliensis in Panama. Rodents, and particularly porcupines, were the second most frequently fed-on mammal by Lu. umbratilis (11.6%) and the Lu. "shannoni" group (8.5%).

Animals↗
PubMed1982

The tree-buttress biotope: a pathobiocenose of Leishmania braziliensis.

A total of 52,033 sandflies, comprising 33 species, was collected in tree buttresses in Panama. Of the 18,025 females collected, 1,592 (8.8%) engorged phlebotomines of 18 species contained sufficient blood for identification of their vertebrate hosts by the microcapillary precipitin method. Lutzomyia ylephiletor and Lu. trapidoi, vectors of Leishmania braziliensis, had fed predominantly on sloths (47.0% and 65.1%, respectively). Lutzomyia shannoni, a common non-anthropophilic sandfly in tree buttresses also fed most frequently on sloths (28.0%) and probably also contributes to the Leishmania transmission cycle among the edentates. Two-toed sloths (Choloepus hoffmanni), the principal reservoir of L. braziliensis in Panama, cohabit the same arboreal bioptope with these sandfly species. Leishmania braziliensis was isolated in culture from 14 of 68 (20.6%) C. hoffmanni captured in the study sites during the period of this investigation. The data illustrate that the butrresses of large trees in Panama represent potential pathobiocenose bioptopes of L. braziliensis. Other sandfly species tested for host-feeding sources included: Lu. trinidadensis, which fed preferentially on reptiles; Lu. triramula, Lu. ovallesi, and Lu. camposi fed most frequently on armadillos. The hosts of 11 additional sandfly species were identified; however, the numbers recorded were too small to discern distinct feeding patterns among the phlebotomines.

Animals↗
PubMed1977

Body weight: its relation to tissue composition, segment distribution, and motor function. I. Interspecific comparisons.

The composition of skin, muscle, and bone and their distribution throughout the body are compared for "advanced" or "specialized" species (Alouatta, Macaca, Canis, Felis, Lepus); smaller, more closely related species (Tupaia and the Lorisidae); and several species within the same ecosystem (Barro Colorado Island, Panama). Among the most significant variables, the skin of sloths, howlers and macaques constitutes more than 12% of body weight, whereas greyhound skin is 5% of weight; sloth and howler muscle are 25% of weight, macaque muscle about 40% of weight, greyhound and agouti muscle over 50% of weight. In tree shrews and galagos muscle is heavier (35%) than in pottos and slow lorises (below 28%), but bone and skin are lighter. All species differ in the segmental distribution of weight. Cats have light tails, light feet and heavy thighs, whereas howlers have heavy tails, heavy feet, and light thighs. The galagos have heavy hindlimbs and tails, the pottos and lorises have reduced tails and approximately equal fore- and hindlimbs. Convergences in segment pattern (sloths with pottos and lorises, marmosets with tree shrews, owl monkeys with galagos, cebus with macaques) as well as divergences are documented. All weight-of tissue and weight-of-segment variables are correlated directly with locomotor adaptation.

Adaptation, Physiological↗
PubMed1987

Heart-lung interaction: effect on regional lung air content and total heart volume.

To study the interactions between and within the heart and lungs, end-diastolic (ED) and end-systolic (ES) volumes and intrathoracic location of the heart, and the regional air content, volume and geometry of the lungs, were measured from three-dimensional image data generated with the Dynamic Spatial Reconstructor (DSR). The DSR was used to scan the full thoracic extent of anesthetized dogs and sloths at selected transpulmonary pressures. The results show that the dependent to nondependent gradient of regional lung opacity (or conversely regional air content) in the supine animal was not present in the prone animals. While the rib cage and diaphragm of the dog deformed markedly, the shape of the sloth's rib cage and diaphragm remained essentially constant with change in body orientation. As a consequence of these findings, we deduce that the observed change in gradient of regional lung air content in both dog and sloth are in response to changes in the intrathoracic position of the heart which alter ventral lung geometry and not a response to changes in rib cage or diaphragm geometry. In a second series of studies we reconstructed the 3-D extent of the heart at ED and ES in supine anesthetized dogs and demonstrated that the total heart volume (THV) (i.e. contained by the pericardial sac) during sinus rhythm differs by less than 5% between ED and ES. The DSR image data show that this is achieved by the epicardial apex remaining essentially fixed and that the plane containing the atrio-ventricular valves moves like a plunger towards the apex in systole. When atrial fibrillation is present, the THV no longer remains constant and decreases during systole, presumably because of increased stiffness of the atrial myocardium. We conclude from the experimental results that the heart plays an important role in determining regional differences in alveolar expansion, and that by maintaining a constant THV, the heart minimizes energy expenditure which would be caused by moving the lung.

Animals↗
PubMed1975

Pneumocystis and Histoplasma infections in wild animals from the Amazon region of Brazil.

Routine examination of tissues from wild forest rodents from Amapá, north Brazil, revealed Pneumocystis carinii in lung smears from a newly captured Oryzomys capito (Cricetidae). Acute, fatal infections with this parasite are also recorded in a number of captive "coatimundis", Nasua narica (Carnivora: Procyonidae) and a sloth, Bradypus tridactylus (Edentata). Pneumocystis was also encountered in lung smears from a newly captured and apparently healthy sloth, Choloepus didactylus. The presence of infection in newly captured animals leads us to believe that the fatal, fulminating pneumocystosis seen in the captive Nasua and Bradypus was due to exacerbation of pre-existant infections acquired in their natural forest environment. Pneumocystis carinii is a well known cause of fatal, interstitial plasma-cell pneumonia in human infants and sometimes the weakened adult: the keeping of exotic pets such as the coatimundi is, therefore, not without some hazard in this respect. Histoplasma, another well known pathogen for man, was isolated from 4 rodents, Proechimys guyanensis (Echimyidae), all from virgin forest along the newly opened Trans Amazon Highway, Pará State, and from a single sloth, Choloepus didactylus, from near Belém, Pará. All these animals showed no symptoms of infection: isolation of the parasite was made by the inoculation of laboratory hamsters with saline suspensions of triturated liver and spleen.

Animals↗
PubMed1983

Distribution and size of Boettcher cells in the little brown bat, rabbit, and other species.

The distribution and size of Boettcher cells were determined from serial sections of the temporal bones of four little brown bats and six rabbits. In addition, one harp seal and one two-toed sloth were examined. In the little brown bat, the heights of the Boettcher cells measured 4-8 micron and they were found throughout much of the length of the cochlea. There were four rows in most of the lower basal coil, five rows in the upper basal coil, and four rows in the middle coil. In the rabbit there were nine rows in the basal coil and 12 rows in the middle coil. The heights of the Boettcher cells were approximately 14 micron in the rabbit. In the two-toed sloth, Boettcher cells were sparsely distributed along the basal coil; similarly, in the harp seal, Boettcher cells were confined solely to the basal coil, where there were only three rows, which measured approximately 18 micron in height. The distribution and size of Boettcher cells in the rabbit and the little brown bat were compared to those in other mammalian species.

Animals↗
PubMed2006

Comparative anatomy and histology of xenarthran osteoderms.

Reconstruction of soft tissues in fossil vertebrates is an enduring challenge for paleontologists. Because inferences must be based on evidence from hard tissues (typically bones or teeth), even the most complete fossils provide only limited information about certain organ systems. Osteoderms ("dermal armor") are integumentary bones with high fossilization potential that hold information about the anatomy of the skin in many extant and fossil amniotes. Their importance for functional morphology and phylogenetic research has recently been recognized, but studies have focused largely upon reptiles, in which osteoderms are most common. Among mammals, osteoderms occur only in members of the clade Xenarthra, which includes armadillos and their extinct relatives: glyptodonts, pampatheres, and, more distantly, ground sloths. Here, I present new information on the comparative morphology and histology of osteoderms and their associated soft tissues in 11 extant and fossil xenarthrans. Extinct mylodontid sloths possessed simple, isolated ossicles, the presence of which is likely plesiomorphic for Xenarthra. More highly derived osteoderms of glyptodonts, pampatheres, and armadillos feature complex articulations and surface ornamentation. Osteoderms of modern armadillos are physically associated with a variety of soft tissues, including nerve, muscle, gland, and connective tissue. In some cases, similar osteological features may be caused by two or more different tissue types, rendering soft-tissue inferences for fossil osteoderms equivocal. Certain osteological structures, however, are consistently associated with specific soft-tissue complexes and therefore represent a relatively robust foundation upon which to base soft-tissue reconstructions of extinct xenarthrans.

Anatomy, Comparative↗
PubMed1996

Megatherium, the stabber.

The traditional point of view that fossil ground sloths (Xenarthra) were a relatively uniform, ecologically little diverse group has been recently challenged. Marine habits have been ascribed to Thalassocnus natans of the Pliocene of Peru. Also, a more diverse diet has been proposed by one of us (R.A.F.) for some Lujanian (late Pleistocene-early Holocene of South America genera of ground sloths. In this paper, an aspect of this latter hypothesis is tested, i.e. that Megatherium americanum had morphological features that are better explained by its having had carnivorous habits rather than by solely herbivorous ones. Specifically, the question of its forearms having been designed for optimizing speed rather than strength of extension is addressed. Such a trait might have been associated with a potentially aggressive use of the animal large claws, whereas a strong extension would be more proper for tearing branches out. On the other hand the high mechanical advantage of the biceps might have made it possible for the animal to have lifted and carried heavy weights. This in turn, suggests the possibility that the animal could have manipulated large prey (for instance, turning dorsally armoured preys or carcasses upside down to expose softer parts and cached large food pieces in a safer place. By this view, Megatherium americanum would be the largest land mammal hunter to have existed.

Animals↗
PubMed1979

Cephalic arterial pattern in New World edentates and Old World pangolins with special reference to their phylogenetic relationships and taxonomy.

The cephalic arterial pattern in edentates and pangolins is described on the basis of 9 corrosion specimens, representing all the classical superfamilies, with special reference to their phylogenetic relationship and taxonomy. In this respect, the importance of the manner in which the external carotid artery system annexes the stepedial area of supply and of the course of the internal carotid artery in relation to the tympanic cavity is emphasized. The investigation does not indicate any special relationship between the New World edentates and the Old World pangolins, whereas the marked difference in the course of the internal carotid artery in recent edentates stresses the independent development of the South American anteaters compared with that of the two other edentate groups (armadillos and tree sloths). Most probably the edentates were divided very early into two main lines which have evolved independently since the early Tertiary, i.e. one for the anteaters and one for the tree sloths and armadillos, indicating a probable subdivision of the true edentates into two suborders. This subdivision is markedly different from the classical two-fold division of the edentates.

Animals↗
PubMed1976

Epidemiological patterns of cutaneous leishmaniasis in Panama. III. Endemic persistence of the disease.

Endemic persistence of cutaneous leishmaniasis is described in El Aguacate, a community established in the forest of central Panama about 75 years ago. Physiographic pecularities partially isolate El Aguacate from other villages in the region. Some of the original forest environment has been preserved and man-biting species of phlebotomine sandflies were abundant as was the two-toed sloth, Choloepus hoffmanni, the principal reservoir host of Leishmania braziliensis in Panama. The inhabitants, as well as their dogs, were examined for natural leishmaniasis in 1969 and 1973. Mammals and phlebotomine sandflies were collected from 1968 to 1973 in a search for reservoir hosts and potential vectors of the disease. Similar studies were undertaken in two nearby villages during 1968 and 1969. L. braziliensis has persisted for many years in El Aguacate, and infection is acquired during childhood. Dogs also were found naturally infected, and the two-toed sloth showed yearly infection rates up to 47.8%. Parasites were demonstrated from a night monkey, Aotus trivirgatus.

Adolescent↗
PubMed1999

Genetic analysis of leishmania parasites in Ecuador: are Leishmania (Viannia) panamensis and Leishmania (V.) Guyanensis distinct taxa?

In the course of an epidemiologic survey in Ecuador, the following collection of Leishmania stocks was isolated: 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either Leishmania (V.) panamensis or L. (V.) guyanensis, 2 stocks were identified as L. (V.) braziliensis, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between L. (V.) braziliensis and L. (V.) guyanensis. These data show that genetic diversity of Leishmania in Ecuador is high and that L. (V.) panamensis/guyanensis is the dominant group in this country. The genetic analysis questioned the distinctness between the two species L.(V.) panamensis and L. (V.) guyanensis, since MLEE and RAPD data did not indicate that L. (V.) panamensis and L. (V.) guyanensis correspond to distinct monophyletic lines. Population genetic analysis performed on the L. (V.) panamensis/guyanensis group favors the hypothesis of a basically clonal population structure.

Animals↗
PubMed1980

Quantitative composition and histological features of the brain in two South American edentates.

The volumes of twelve brain components relative to body weights in the armadillo and the tree-sloth have been estimated. The progression of each component with respect to a basal reference type is indicated. The armadillo shows the brain organization of a little evolved mammal with developed olfactory structures and a large pyriform lobe in particular. The sloth possesses a more advanced type of brain with an unexpectedly voluminous neocortex. Some behavioural features probably correlated to the size of brain structures in those Edentates are mentioned and the need for a reconsideration of the concept of primitiveness is stressed.

Animals↗
PubMed1994

Combined occurrence of trypanosomal sialidase/trans-sialidase activities and leishmanial metalloproteinase gene homologues in Endotrypanum sp.

Endotrypanum (order Kinetoplastida: family Trypanosomatidae) is a parasite of forest dwelling tree sloths (Edentata: genera Choleopus and Bradypus). Unique among the haemoflagellates, this protozoan has an intraerythrocytic phase in the mammalian host. Nevertheless, many striking similarities exist between Endotrypanum and the human pathogen Leishmania that make it a useful model for epidemiological and evolutionary aspects of the biology of trypanosomatids. Importantly, Endotrypanum species share both the insect vector and host reservoir with certain species of Leishmania (subgenus Viannia). Because mixed infections with Endotrypanum and Leishmania are common in sloths and, therefore, likely to occur in the sandfly vector, there is a need for adequate biochemical markers to distinguish Endotrypanum from Leishmania infections. In this paper we show that Endotrypanum promastigotes possess sialidase and trans-sialidase activities, which are absent from Leishmania, and which are not closely related to the previously described trypanosomal sialidase/trans-sialidase enzyme. We also document the occurrence in Endotrypanum of homologues of the leishmanial surface metalloproteinase gp63 genes. The combined occurrence of sialidase/trans-sialidase activities and gp63 gene homologues in a unique organism has important ramifications for both field and laboratory studies on the biology of trypanosomatids, especially those related to host infection and evolution.

Animals↗
PubMed2004

Phylogeny of the bears (Ursidae) based on nuclear and mitochondrial genes.

The taxomic classification and phylogenetic relationships within the bear family remain argumentative subjects in recent years. Prior investigation has been concentrated on the application of different mitochondrial (mt) sequence data, herein we employ two nuclear single-copy gene segments, the partial exon 1 from gene encoding interphotoreceptor retinoid binding protein (IRBP) and the complete intron 1 from transthyretin (TTR) gene, in conjunction with previously published mt data, to clarify these enigmatic problems. The combined analyses of nuclear IRBP and TTR datasets not only corroborated prior hypotheses, positioning the spectacled bear most basally and grouping the brown and polar bear together but also provided new insights into the bear phylogeny, suggesting the sister-taxa association of sloth bear and sun bear with strong support. Analyses based on combination of nuclear and mt genes differed from nuclear analysis in recognizing the sloth bears as the earliest diverging species among the subfamily ursine representatives while the exact placement of the sun bear did not resolved. Asiatic and American black bears clustered as sister group in all analyses with moderate levels of bootstrap support and high posterior probabilities. Comparisons between the nuclear and mtDNA findings suggested that our combined nuclear dataset have the resolving power comparable to mtDNA dataset for the phylogenetic interpretation of the bear family. As can be seen from present study, the unanimous phylogeny for this recently derived family was still not produced and additional independent genetic markers were in need.

Animals↗
PubMed1986

Extinction of Harrington's mountain goat.

Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 +/- 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters.

Journal Article↗
PubMed1986

Protein sequence evidence for monophyly of the carnivore families Procyonidae and Mustelidae.

The amino acid sequence of the eye lens protein alpha-crystallin A of the ring-tailed cat, Bassariscus astutus, has been determined. The sequence of the Bassariscus alpha A chain, which is 173 residues long, was compared with the previously determined set of 41 mammalian alpha A sequences. Among the investigated carnivores (dog, cat, sloth bear, American mink, gray seal, and California sea lion) the Bassariscus alpha A sequence exclusively shares two amino acid replacements with the alpha A chain of the mink, Mustela vison: 7 His----Gln and 61 Ile----Val. The Mustela and Bassariscus alpha A sequences differ at only three positions and have no replacements in common with any of the other investigated carnivore alpha A chains. Furthermore, the replacement 7 His----Gln has only been found in three-toed sloth, whereas 61 Ile----Val occurs scattered in three other taxa: pig, rhinoceros, and prosimians. It thus is most parsimonious to join Bassariscus and Mustela--and consequently their respective families, Procyonidae and Mustelidae--as sister groups in the phylogenetic tree of mammalian alpha A sequences.

Amino Acid Sequence↗
PubMed1999

Effects of inedible, manipulable objects on captive bears.

Bears in captivity often show abnormal behaviors such as stereotypies and periods of excessive inactivity. Most of the research aimed at reducing abnormal behaviors in bears has focused on feeding enrichment. However, the effects of feeding enrichment only seem to last as long as it takes a bear to consume the food. This study investigated the effects of inedible, manipulable objects on bears. Two polar bears (Ursus maritimus) received plastic floats. A sloth bear (Melursus ursinus) and a spectacled bear (Treniarctos ornatus) received plastic balls. During a 7-week period, polar bears nearly doubled their activity in the presence of toy floats, and the spectacled bear halved its pacing in the presence of toys. The sloth bear did not respond to the objects. These findings indicate that access to manipulable nonfood objects such as plastic toys can result in prolonged engagement in appetitive behaviors by polar bears.

Journal Article↗