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PubMed1983

The autonomic component in blood pressure and heart rate effects of tilting in the three-toed sloth.

1. This study attempts to elucidate unique heart and blood pressure responses seen in sloths in response to tilting by blocking autonomics with atropine, propranolol, or a combination of these. 2. Atropine produces less heart rate increase in sloths than in other mammals but blocks reflex bradycardia as expected. 3. Propranolol reduces heart rate to about the same degree as in man and completely blocks all cardiac responses to tilting, both direct and reflex. 4. Atropine slightly diminishes blood pressure responses to tilting whereas propranolol tends to augment the already marked increases.

Animals↗
PubMed1987

Responses of the three-toed sloth, Bradypus tridactylus, to some commonly used pharmacologic agents. I. Autonomic drugs.

1. Sloths are very responsive to epinephrine and norepinephrine; i.v. injection of 1 microgram/kg elevates systolic pressure 80 and 90% respectively. 2. Doses as low as 0.01 microgram/kg of epinephrine as well as norepinephrine raise diastolic pressure. 3. Similarity of effects of these catecholamines can be explained on the basis of the low proportion of skeletal muscle (35 vs 45% in most mammals) and a small liver which reduces the proportion of beta 2 dilators to alpha constrictors responding to epinephrine. 4. Slowness of reflexes allows clear separation of early (0-20 sec), direct accelerating heart rate effect (up 15% with 1 microgram/kg of norepinephrine) and later (20-60 sec), reflex bradycardia (down 30% from control level). 5. Sloths are more sensitive to the vasodilating effects of isoproterenol or less sensitive to beta 1 cardiac stimulating effects than most laboratory mammals; doses as low as 0.1 microgram/kg cause a fall in mean arterial pressure not overcome by increased heart rate.

Animals↗
PubMed2006

Stomach lysozymes of the three-toed sloth (Bradypus variegatus), an arboreal folivore from the Neotropics.

Lysozymes are antimicrobial defences that act as digestive enzymes when expressed in the stomach of herbivores with pre-gastric fermentation. We studied this enzyme in the complex stomach of the three-toed sloth (Bradypus variegatus), a folivore with pre-gastric fermentation. Lysozymes were identified by SDS-PAGE and immunoblotting in all portions: diverticulum, pouch, glandular and muscular prepyloric area with 14.3 kDa of molecular mass. Purified lysozymes from all areas but the diverticulum were characterized by MALDI-TOF, optimal pH, optimal ionic strength, and specific activity. The differences observed suggested at least three isoforms. The optimal pHs were similar to the pH of the stomach portion where the enzymes were isolated. The lysozyme from the pouch (fermentation chamber) exhibited higher specific activity and concentration than the others. The specific activity of the enzyme from the acid muscular prepyloric portion was comparable to that reported in the cow abomasums; however, its concentration was lower than that observed in cow. This distinctive pattern of secretion/specific activity and overall low concentration suggests different roles for the lysozymes in this herbivore compared to Artiodactyla. We postulate that sloth stomach lysozymes may still be antimicrobial defences by protecting the microbial flora of the fermentation chamber against foreign bacteria.

Animals↗
PubMed2002

Dwarfism in insular sloths: biogeography, selection, and evolutionary rate.

The islands of Bocas del Toro, Panama, were sequentially separated from the adjacent mainland by rising sea levels during the past 10,000 years. Three-toed sloths (Bradypus) from five islands are smaller than their mainland counterparts, and the insular populations themselves vary in mean body size. We first examine relationships between body size and physical characteristics of the islands, testing hypotheses regarding optimal body size, evolutionary equilibria, and the presence of dispersal in this system. To do so, we conduct linear regressions of body size onto island area, distance from the mainland, and island age. Second, we retroactively calculate two measures of the evolutionary rate of change in body size (haldanes and darwins) and the standardized linear selection differential, or selection intensity (i). We also test the observed morphological changes against models of evolution by genetic drift. The results indicate that mean body size decreases linearly with island age, explaining up to 97% of the variation among population means. Neither island area nor distance from the mainland is significant in multiple regressions that include island age. Thus, we find no evidence for differential optimal body size among islands, or for dispersal in the system. In contrast, the dependence of body size on island age suggests uniform directional selection for small body size in the insular populations. Although genetic drift cannot be discounted as the cause for this evolution in body size, the probability is small given the consistent direction of evolution (repeated dwarfism). The insular sloths show a sustained rate of evolution similar to those measured in haldanes over tens of generations, appearing to unite micro- and macroevolutionary time scales. Furthermore, the magnitude and rate of this example of rapid differentiation fall within predictions of theoretical models from population genetics. However, the linearity of the relationship between body size and island age is not predicted, suggesting that either more factors are involved than those considered here, or that theoretical advances are necessary to explain constant evolutionary rates over long time spans in new selective environments.

Animals↗
PubMed1961

Spinal reflexes and seizure patterns in the two-toed sloth.

In striking contrast to the seizure patterns of other animals, the electroshock seizure of the sloth consists of weak extension followed by tonic flexion and terminal clonus. A similar pattern is seen with direct spinal cord stimulation. Strychnine produces a pure flexor convulsion. In the spinal sloth, painful stimulation of one foot causes extension at some joints of that limb and strong flexion at all joints of the contralateral limb.

Animals↗
PubMed1989

The primary structure of pale-throated three-toed sloth (Bradypus tridactylus, Xenarthra) hemoglobin.

The hemoglobin of the Pale-Throated Three-Toed Sloth (Bradypus tridactylus, Xenarthra) was separated into two components (ratio 4:1) with identical amino-acid analyses for the alpha- and beta-chains. The primary structures of both chains from the major component are given. They could be isolated by chromatography on carboxymethyl cellulose CM-52. The sequences have been determined by automatic Edman degradation of the native chains and their tryptic peptides. The comparison with human hemoglobin showed 27 substitutions in the alpha-chains and 33 in the beta-chains. In the alpha-chains one amino-acid exchange involves an alpha 1/beta 1-contact. In the beta-chains two heme- and four alpha 1/beta 1-contacts are substituted. The hemoglobin of the Sloth is compared to that of the Nine-Banded Armadillo (Dasypus novemcinctus), another representative of the order Xenerthra.

Amino Acid Sequence↗
PubMed2003

Brazilian distribution of Amblyomma varium Koch, 1844 (Acari: Ixodidae), a common parasite of sloths (Mammalia: Xenarthra).

Amblyomma varium, commonly known in Brazil as the "carrapato-gigante-da-pregui a" (sloth's giant tick) is found from southern Central America to Argentina. The present study adds information on the geographical distribution of A. varium, as well as on their hosts, based on material deposited in the main Brazilian collections and on the available literature. Eighty-two vials, containing 191 adult specimens, deposited in five Acari collections between 1930 and 2001, were examined. These vials included data on the host and collection localities. The biology of A. varium is unknown. However it is known that, during the adult stage, the tick presents a high host specificity and is found almost exclusively on the sloths Bradypus tridactylus, B. variegatus, B.torquatus (Bradypodidae), Choloepus hoffmanni and C. didactylus (Megalonychidae). Based on the material examined, the states of Rond nia, Amazonas, Bahia and Alagoas are newly assigned to geographic distribution of A. varium in Brazil.

Animals↗
PubMed2000

An update on the physiology of two- and three-toed sloths.

Physiological and pharmacological research undertaken on sloths during the past 30 years is comprehensively reviewed. This includes the numerous studies carried out upon the respiratory and cardiovascular systems, anesthesia, blood chemistry, neuromuscular responses, the brain and spinal cord, vision, sleeping and waking, water balance and kidney function and reproduction. Similarities and differences between the physiology of sloths and that of other mammals are discussed in detail.

Anesthesia↗
PubMed2003

Circadian rhythms in blood pressure in free-ranging three-toed sloths (Bradypus variegatus).

Blood pressure (BP) profiles were monitored in nine free-ranging sloths (Bradypus variegatus) by coupling one common carotid artery to a BP telemetry transmitter. Animals moved freely in an isolated and temperature-controlled room (24 degrees C) with 12/12-h artificial light-dark cycles and behaviors were observed during resting, eating and moving. Systolic (SBP) and diastolic (DBP) blood pressures were sampled for 1 min every 15 min for 24 h. BP rhythm over 24 h was analyzed by the cosinor method and the mesor, amplitude, acrophase and percent rhythm were calculated. A total of 764 measurements were made in the light cycle and 721 in the dark cycle. Twenty-four-hour values (mean +/- SD) were obtained for SBP (121 +/- 22 mmHg), DBP (86 +/- 17 mmHg), mean BP (MBP, 98 +/- 18 mmHg) and heart rate (73 +/- 16 bpm). The SBP, DBP and MBP were significantly higher (unpaired Student t-test) during the light period (125 +/- 21, 88 +/- 15 and 100 +/- 17 mmHg, respectively) than during the dark period (120 +/- 21, 85 +/- 17 and 97 +/- 17 mmHg, respectively) and the acrophase occurred between 16:00 and 17:45 h. This circadian variation is similar to that observed in cats, dogs and marmosets. The BP decreased during "behavioral sleep" (MBP down from 110 +/- 19 to 90 +/- 19 mmHg at 21:00 to 8:00 h). Both feeding and moving induced an increase in MBP (96 +/- 17 to 119 +/- 17 mmHg at 17:00 h and 97 +/- 19 to 105 +/- 12 mmHg at 15:00 h, respectively). The results show that conscious sloths present biphasic circadian fluctuations in BP levels, which are higher during the light period and are mainly synchronized with feeding.

Analysis of Variance↗
PubMed2005

Electrocardiographic studies of the three-toed sloth, Bradypus variegatus.

Electrocardiograms (ECG) obtained with standard limb leads and augmented unipolar limb leads were recorded from 17 unanesthetized adult sloths. The animals were held in their habitual position in an experimental chair. We determined heart rate and rhythm from the R-R intervals, the amplitude and duration of each wave, and the duration of the segments and intervals of the ECG. The mean electrical axes of P and T waves and QRS complex were calculated on the basis of the amplitude of these waves in leads I, II, III, aV R, aV L, and aV F. The P wave appeared positive in most tracings with low amplitude in lead II, the QRS complex was generally negative in leads aV R, III and aV F, and no arrhythmias were observed. With a mean +/- SD heart rate for all recordings of 81 +/- 18 bpm, the duration of P and T waves, QRS complex, and PR, QT and RR intervals averaged 0.05 +/- 0.02, 0.15 +/- 0.05, 0.07 +/- 0.02, 0.13 +/- 0.02, 0.38 +/- 0.04, and 0.74 +/- 0.17 s, respectively. The ECG shape had a definite configuration on each lead. The angles of the mean +/- SD electrical axes for atrial and ventricular depolarization and ventricular repolarization in the horizontal plane were +34 +/- 68 masculine, -35 +/- 63 masculine, and -23 +/- 68 masculine, respectively. All electrical axes showed great variations and their mean values suggest that, when the sloth is in a seated position, the heart could be displaced by the diaphragm to a semi-horizontal position.

Animals↗
PubMed1980

Leishmania braziliensis in the Panamanian two-toed sloth, Choloepus hoffmanni.

A total of 498 two-toed sloths, Choloepus hoffmanni, collected in central Panama was examined for Leishmania braziliensis over a 10-year period. Isolations of the parasite from 96 (19.3%) of the animals were confirmed by culture and inoculation of golden hamsters. Improved culture techniques developed toward the end of the study assisted in determining a greater prevalence of the disease. Infectins were completely cryptic in all animals, and the parasite was isolated from skin, blood, liver, spleen, bone marrow and lung tissues. Sloths maintained under seminatural conditions remained infected up to 23 months, the longest period of survival. This edentate, considered the principal reservoir host of L. braziliensis in Panama, showed infection rates from 0-59.4% in various communities, which appeared to correlate with the parasite prevalence in the indigenous human populations.

Age Factors↗
PubMed1999

Clinical problems of sloths (Bradypus sp. and Choloepus sp.) in captivity.

A 20-yr retrospective study of disease prevalence was carried out for 51 sloths (34 Bradypus sp. and 17 Choloepus sp.) at the São Paulo Zoo. A total of 81 clinical disorders were detected, including nutritional (45.7%), digestive (12.3%), and respiratory (12.3%) problems and injuries (6.1%). A definitive diagnosis was not possible in 8.6% of the cases. The incidence of disease varied according to seasonal climate (winter, 32.5%; spring, 24%; summer, 22.9%; autumn, 20.5%), time in captivity (96.4% of diseases occurred within the first 6 mo and 3.6% occurred thereafter), and type of enclosure (quarantine cage, 96.4%; exhibition enclosure, 3.6%). Both young animals (86.7%) and adults (3.2%) were affected. Parasites were identified by fecal examination in 45.4% of animals with clinical illness (Ascaris sp., 80%; Coccidia sp., 20%). Bacteria such as Salmonella enteritidis, Escherichia coli, and Citrobacter freundii were isolated from feces and/or organs. The first 6 mo in captivity are critical for these animals. Proper management and early identification of medical conditions in captivity have implications for sloth population in the wild.

Animals↗
PubMed1989

Ganglion cell size and distribution in the retina of the two-toed sloth (Choloepus didactylus L.).

The distribution of ganglion cell densities and sizes was studied in Nissl-stained flat-mount retinae of the two-toed sloth. The area centralis, a weak specialization with low ganglion cell density, is located in the temporal retina close to the center of the eye. The presence of a visual streak was noted. The distribution of different ganglion cell sizes was approximately equal throughout the retina. Although the retinal organization differs from that of the closely related three-toed sloth, the presumed function of retinal specializations in both species is to guide limb movements by permitting visualization of the branch along which the animal is climbing.

Adaptation, Physiological↗
PubMed1984

Ventricular fibrillation threshold in the three-toed sloth (Bradypus tridactylus).

The ventricular fibrillation threshold (VFT) can be defined as the minimum electrical value able to trigger fibrillation. The objective was to determine the threshold fibrillatory current in the three-toed sloth, animal which may show spontaneous defibrillation. Ten specimens were used (average weight 3.9 kg, SD 0.28). Two electrodes of the spoon type were laterally applied to the ventricles, stimulating with a nonsynchronized train of rectangular pulses, variable amplitude, until fibrillation was established. Applied voltage and current were displayed on a storage oscilloscope. The average VFT current was 2.3 mA/g of heart (SD 0.4). Each threshold was obtained as the mid-range value between the maximum current which did not fibrillate and the minimum one which did fibrillate. Out of 98 fibrillations, 40% showed spontaneous reversal before 60 sec of fibrillation were completed. Beyond that time, electrical defibrillation was instituted. Three puppies (average weight 5.2 kg, SD 1.4) yielded an average VFT of 0.59 mA/g of heart (SD 0.14) using the same procedure. When the two VFT were compared (unpaired "t"-test), a significant difference was found (t 6.35; p less than 0.001), concluding that sloths would appear as more difficult to fibrillate than dogs of comparable body size.

Animals↗
PubMed2004

Economic interventions to promote physical activity: application of the SLOTH model.

Physical inactivity is responsible for major health and economic costs in the United States. Despite widespread recognition of the scope and importance of the problem of physical inactivity, only modest progress has been made in improving overall physical activity in the U.S. population. This paper applies a combined economic and public health perspective to better understand physical activity behavior and to guide a search for promising new economically oriented interventions to increase physical activity at the population level. This perspective is operationalized as the SLOTH model-a time-budget model incorporating Sleep, Leisure, Occupation, Transportation, and Home-based activities. Key economic forces that may influence individuals' choices about utilization of time and physical activity are identified. Potential interventions are proposed in response to each of the important forces and are evaluated on four criteria: (1) economic efficiency, (2) equity, (3) effectiveness, and (4) feasibility. The SLOTH model provides guidance regarding interventions that might increase physical activity in each of the four nonsleep domains. Economic intervention strategies are proposed and compared to economic and public health criteria. The results provide a starting point for selecting and evaluating potentially effective and feasible economic interventions that might be implemented as part of a larger effort to address the health crisis of inactive lifestyles and obesity.

Exercise↗
PubMed1986

Sloth bear immobilization with a ketamine-xylazine combination: reversal with yohimbine.

Five captive sloth bears (Melursus ursinus) were immobilized with a combination of ketamine (5.80 to 9.75 mg/kg of body weight) and xylazine (1.40 to 2.44 mg/kg), given IM. The youngest bear was immobilized twice, 62 days apart; all other bears were immobilized only once. Induction times were 4 to 25 minutes. After completion of various intended procedures, yohimbine (0.125 mg/kg) was administered IV. Arousal times were 2 to 20 minutes and bears were standing in 17 to 51 minutes. Compared with reported recovery times of 2 to 3 hours for bears immobilized with ketamine-xylazine combinations but not given an antagonist, results of the present study indicated that yohimbine reduces anesthesia recovery times in sloth bears immobilized with ketamine-xylazine combination.

Animals↗
PubMed1990

Ultrastructural study of crystalloids in Sertoli cells of the three-toed sloth (Bradypus tridactylus).

Crystalloids were found in Sertoli cells of the testis of the three-toed sloth by examination at the light- and electron-microscopic levels. Needle-, or spindle-shaped crystalloids, varying in length, were located in the basal part of the Sertoli cells. They consisted of bundles of filaments each measuring approximately 11 nm in diameter. Several filaments were packed hexagonally to form a bundle. The center-to-center distance between individual filaments of a bundle was approximately 17 nm. Periodical lateral projections emanated from the filaments. Cross sections of crystalloids showed that the projections radiated from each filament in three directions, forming an equilateral triangle with a side length of approximately 15 nm. Scattered polyribosomes were found between and around the bundles.

Animals↗
PubMedDate not supplied

Survey of distribution of substance P, vasoactive intestinal polypeptide, cholecystokinin, neurotensin, Met-enkephalin, bombesin and PHI in the spinal cord of cat, dog, sloth and monkey.

Levels of substance P (sP), peptide-histidine-isoleucine (PHI), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), neurotensin (NT), bombesin (BOM) and methionine-enkephalin (Met-Enk) like immunoreactivity were measured in cat, dog, primate and sloth cervical, thoracic, lumbar and sacral dorsal and ventral horns and dorsal root ganglia. The levels of peptides in the cat sacral cord and the principal peaks of immunoreactivity on a 10-60% acetonitrile gradient on a C18 reverse phase high performance liquid chromatography (HPLC) were sP (sP1-11: 369 ng/g), PHI (PHI: 271 ng/g), VIP (VIP1-28: 210 ng/g), Met-Enk (Met1-5 and extended forms: 257 ng/g), BOM (BOM1-10 and GRP1-27: 20 ng/g), CCK (CCK-8: 15 ng/g) and NT (NT1-13: 10 ng/g). Consideration of the rostrocaudal levels revealed an approximately even distribution with the exception of VIP and PHI which showed sacral/cervical ratios of 79 and 63. For sP, Met-Enk and BOM dorsal/ventral ratios were greater than 1 at all spinal levels. For VIP, PHI and CCK these ratios were greater than 1 only in the sacral cord. Dorsal root ganglion (DRG) levels of sP, VIP, PHI were readily measurable in single ganglia and covaried with the respective levels in the dorsal cord. Pooled samples of spinal ganglia and the trigeminal ganglia revealed that the relative levels of peptide immunoreactivity were: sP (25 ng/g); VIP (26 ng/g); PHI (28 ng/g); Met-Enk (6 ng/g); CCK (2 ng/g); NT (1 ng/g); and BOM (1 ng/g).

Animals↗