Choloepus Hoffmanni Research Articles

A better technic for the study of male meiosis and particularly the mode of association of sex chromosomes

An improved technique for the study of meiosis is described. The principle is based on the use of Ca- and Mg- free isotonic salt solution buffered with phosphates and of hypotonic medium without citrate. Thousands of meiotic randomly dispersed prophases may be observed in good conditions regarding not only the preservation and spreading of autosomic bivalents but also the mode of association between the X and Y inside the sex vesicle. In the Rat, it seems clear that inside the sex vesicle in pachytene the Y (heterochromatic) and the X (not heterochromatic) chromosomes are already associated “end to end” and that there is no chiasmatic relation between them. In diplotene, the Y chromosome has been seen associated by its non-centromeric end, the X, apparently by its short-arms end. The question to know whether this kind of association is peculiar to the Rat or may be generalized to all placental mammals is still under investigation. In the Sloth (Choloepus hoffmanni), the normal translocation of the Y on an autosome is cleary, demonstrable during meiosis as a peculiar type of association (trivalent).

The spinal roots in the sloth (Choloepus hoffmanni peters)

AbstractIn the lower half of the thoracic region in Choloepus hoffmanni, a didactyl sloth, which possesses 23 dorsal vertebrae, the spinal roots assume a rostralward direction. This situation raises difficult problems in early embryological development as it already prevails — although slightly altered — in the 100 gm foetus. The myelinated nerve fiber diameters in the ventral roots are smaller than in the cat. This conforms to the general rule that “red” and slow muscle fibers are supplied by thinner motor fibers than the “white” fast muscles, because in the sloth the whole of the musculature is of the former type. The γ efferent system is well developed. The sympathetic preganglionic fibers are thought to be mostly unmyelinated. From the fiber spectrum in the dorsal roots it appears that the muscle spindle afferents are also of smaller diameter than in the cat. The cuscle spindles, the sympathetic chain and the aortic origin of the intercostal arteries are described.

Relation of properties of isolated myosin to those of intact muscles of the cat and sloth.

Myosin was prepared from the extensor digitorum longus, gastrocnemius medialis and lateralis, tibialis anterior, flexor of the claws of the anterior limb, and diaphragm muscles of the cat and didactyl sloth (Choloepus hoffmanni Peters). Actin‐activated, Ca2+‐activated, and EDTA‐activated ATPase activities of the myosins from cat muscles were two to four times higher than those of the myosins from the same muscles of the sloth. The difference in the Ca2+‐activated ATPase activity was found in the pH range of 5.5 to 10.0, and in the KCl concentration range of 50 mM to 500 mM at pH 7.0.The kinetic characteristics of the two myosins indicated that both the Km and the Vmax of the ATPase activities of the sloth myosin were lower than those of cat myosin by a factor of several‐fold.Reconstituted cat actomyosin superprecipitated four to six times faster than sloth actomyosin. This difference in the superprecipitation did not vary appreciably when the concentration of ATP and the ratio of myosin to actin were varied. A correlation between the ATPase activity and the speed of superprecipitation of actomyosins of the cat and sloth was shown.The contraction time of various muscles of the cat and sloth was found to be inversely proportional to the actin‐activated ATPase activity of their respective myosins. The speed constant of shortening of the muscles of the diaphragm appeared to be proportional to the actin‐activated ATPase activity of their myosin.In contrast to the ATPase activity of myosin, which varied according to the speed of contraction, the actin‐binding ability of myosins of the cat and sloth was rather constant. The extent of superprecipitation of various reconstituted actomyosins of the cat and sloth was also the same. These properties of the isolated myosins were related to the similar tension output of the muscles of the cat and sloth.

Spinal roots in the sloth.

IN the course of an investigation intended to relate the size of the myelinated motor nerve fibres to the speed of the muscles in Choloepus hoffmanni Pet.1, in which the whole musculature is ‘red’ in character, we were struck by the unusual arrangement of the spinal roots. It is generally assumed that the backward obliquity of the spinal roots in adult mammals is due to a differential rate of growth of the spinal cord and of the vertebral column. In man, this obliquity increases from the second cervical root to the filum terminale. In cat, dog and sheep, the obliquity of the D13–L2 roots is reduced, but more caudally the roots resume their strong backward direction. In the ox, a similar alteration in the course of the spinal roots leads to a situation where the tenth and eleventh dorsal roots are at right angles to the spinal cord. In the horse, which has 18 dorsal vertebrae, the oblique run of the spinal roots starts from D2 decreases from D11 to D17 and then increases again2.

A Trypanosoma cruzi-like trypanosome in the coati ( Nasua narica) from British Honduras

Theory predicts that mating systems are influenced by sex-specific selection pressures and the dispersion of females, but potential constraints imposed by a species' life history and physiology are rarely considered. Sloths, or ‘perezosos’ (the ‘lazies’) in Spanish, are one of the most sedentary terrestrial mammals on Earth, and we hypothesized that their low mobility would constrain the ability of males to take advantage of the ‘polygamy potential’ of their environment. We characterized the reproductive strategy of Hoffmann's two-toed sloths, Choloepus hoffmanni, in an agro-ecosystem in northeastern Costa Rica by assigning paternity, characterizing the spatial distribution of related individuals and describing the space use of 157 individuals. Spatial patterns of relatedness suggested that natal dispersal was female biased and sufficient to avoid inbreeding. Five (36%) adult males sired offspring with more than one female, and we observed three apparent extraterritorial matings, indicating that sloths were not strictly monogamous. Generally, adult males were segregated and appeared to show some territoriality in core areas, although home ranges of adjacent males overlapped in areas of low use. On average, male home ranges encompassed more than three females, and females usually occurred within the home range of more than one male. These patterns of space use and relatedness suggest males monopolize space more than they do females, and that the mating system of Hoffmann's two-toed sloth involves a mixture of polygyny and promiscuity. Neighbouring males were more closely related than expected, suggesting that a certain level of tolerance among males may stem from the benefits of kin selection and the limited ability of males to monopolize breeding opportunities.

A Sarcocystis species in a two-toed sloth, Choloepus hoffmanni hoffmanni, from Central America

A Sarcocystis species in a two-toed sloth, Choloepus hoffmanni hoffmanni, from Central America

Contribución al estudio de Endotrypanum schaudinni (Trypanosomidae)

A chronological review of the existing literature on Endotrypanum schaudinni MESNIL and BRIMONT 1908 is made. An arrangement of the existing knowledge on these interesting trypanosomes is attempted and further facts are contributed. The taxonomic position and characteristics of their vertebrate hosts, Bradypus and Choloepus, is given as well as some observations on the biology and geographical distribution on the specimens captured this country. The morphology of the parasite has been observed both fresh as well as stained preparations, and trypanosome forms have been reported Choloepus hoffmanni for the first time. Intracellular forms are reported only those slides which were prepared immediately after obtaining the blood. The technique and the different culture media employed the primary isolation of the hemoparasite are given. The harmful effects of anti-clotting agents the culture media is noticed. A study of the culture forms is carried out both on fresh as well as on stained preparations, reporting our strains only the leshmania and leptomona forms. A comment is made relation to the trypanosome forms that had been reported by CUNHA and MUNIZ (4). Different laboratory animals were inoculated with blood of infected Choloepus and with culture forms without being able to demonstrate infection any of them, probably due to their great specificity toward edentates inferred easily from their strict intracellular parasitism. In addition, comments are made on the importance of the physiological state of the animals to be inoculated. An adult Choloepus and a human being were inoculated with fresh culture forms but negative results were obtained. This might be due to a 1055 of virulence of the in vitro strain or to a state of premunition of the adult specimen to a protozoosis. Recently isolated culture forms were inoculated into the vitellin sac of the chick embryo with negative results. With respect to its evolutive cycle, the parasite does not present division forms the peripheral blood stream nor were its tissular forms found the histological examination. The finding of parasite nests a breast of Bradypus griseus griseus does not make its evolution the vertebrate host any clearer to us due to the fact that the sloth was parasitized with another trypanosome and that the presence of a kinetoplast could not be demonstrated these forms, all of which suggests the possibility of a toxoplasmosis. In exalated blood kept at room temperature the parasites leave the erythrocytes and show a better locomotive apparatus. This we relate to its evo­lutive cycle since this phenomenon probaly takes place the intestinal tract of some intermediary arthropod host. Several ectoparasites were collected from Choloepus, among them a tick of the genus Amblyomma. In Bradypus, several arthropods that live intimate relationship with this vertebrate are reported, such as Cryploses choloepi, among them a tick of the genus Amblyomma. In Bradypus, several arthropods that live intimate relationship with this vertebrate are reported, such as Cryptoses choloepi, Trichillum bradyporum, and a coleopterus of the family Scarabeidae. In addition, Amblyomma gertschi was found and was carefully studied since it was the only hematophagous ectoparasite. An unsuccesful effort is made at finding a hemipterus, Belminus costa­rincensis, that had been reported a sloth. Although the search for the vector of this parasitosis was fruitless, we are convinced of its existence and will continue searching for it. We carried out a xenodiagnosis on Choloepus, with Triatoma infestans and Triatoma dimidiata, without being able to obtain the evolution of the parasite. The main characteristics of the genus Endotrypanum are given but it cannot be definitely placed the family Trypanosomidae since its evolutive cycle is not known.

Correlation between serum protein-bound iodine levels and metabolic rates in male bovine.

ArticleCorrelation Between Serum Protein-Bound Iodine Levels and Metabolic Rates in Male BovineK. H. Burns, R. W. Colby, Priscilla Gougler, and H. O. KunkelK. H. BurnsFrom the Department of Biochemistry and Nutrition Texas Agricultural and Mechanical College System, College Station, Texas, R. W. ColbyFrom the Department of Biochemistry and Nutrition Texas Agricultural and Mechanical College System, College Station, Texas, Priscilla GouglerFrom the Department of Biochemistry and Nutrition Texas Agricultural and Mechanical College System, College Station, Texas, and H. O. KunkelFrom the Department of Biochemistry and Nutrition Texas Agricultural and Mechanical College System, College Station, TexasPublished Online:31 Dec 1952https://doi.org/10.1152/ajplegacy.1952.172.1.107MoreSectionsPDF (277 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat "Correlation Between Serum Protein-Bound Iodine Levels and Metabolic Rates in Male Bovine." American Journal of Physiology-Legacy Content, 172(1), pp. 107–108 Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByLa fonction thyroidienne chez l'unau (Choloepus hoffmanni Peters)General and Comparative Endocrinology, Vol. 12, No. 2Thyroid metabolism in sheep during pregnancy27 March 2009 | The Journal of Agricultural Science, Vol. 52, No. 1Energy Investigations as Related to Fetus Formation in CattleActa Agriculturae Scandinavica, Vol. 7, No. 1 More from this issue > Volume 172Issue 1December 1952Pages 107-108 Copyright & PermissionsCopyright © 1952 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1952.172.1.107History Received 1 October 1952 Published online 31 December 1952 Published in print 31 December 1952 Metrics

RETICULO-SPINAL INFLUENCES ON STRETCH REFLEXES

ArticlesRETICULO-SPINAL INFLUENCES ON STRETCH REFLEXESJames M. Sprague, L. H. Schreiner, D. B. Lindsley, and H. W. MagounJames M. Sprague, L. H. Schreiner, D. B. Lindsley, and H. W. MagounPublished Online:01 Nov 1948https://doi.org/10.1152/jn.1948.11.6.501MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByNeuronal activities of the vestibular nuclear complex during mechanically induced rhythmic jaw movements in ratsBrain Research Bulletin, Vol. 89, No. 3-4Motor control in sleepContributions of Altered Stretch Reflex Coordination to Arm Impairments Following StrokeRandy D. Trumbower, Vengateswaran J. Ravichandran, Matthew A. Krutky, and Eric J. Perreault1 December 2010 | Journal of Neurophysiology, Vol. 104, No. 6Modulation of the masseteric monosynaptic reflex by stimulation of the vestibular nuclear complex in ratsNeuroscience Letters, Vol. 466, No. 1James M. SpragueInhibition of Spinal Reflexes by Paramedian Reticular NucleusBrain Research Bulletin, Vol. 25, No. 4Facilitation of lumbar monosynaptic reflexes by locus coeruleus in the ratBrain Research, Vol. 369, No. 1-2Neural Mechanisms of Female Reproductive BehaviorLocus Coeruleus Control of Spinal Cord ActivitySuppression of Bulboreticular Unit Responses to Noxious Stimuli by Analgesic Mesencephalic Stimulation10 July 2009 | Somatosensory Research, Vol. 1, No. 2CONCLUDING REMARKSControl of Motoneuron Output by Pathways Descending from the Brain StemBehavioral functions of the reticular formationBrain Research Reviews, Vol. 1, No. 1Activation, Coping, and PsychosomaticsThe influence of different descending systems on the tonic stretch reflex in the catExperimental Neurology, Vol. 37, No. 3Activity of vestibulospinal neurons during locomotionBrain Research, Vol. 46Effects of electric stimulation of brain stem reticular formation on hippocampal theta rhythm and muscle activity in unanesthetized, cervical- and midbrain-transected ratsBrain Research, Vol. 41, No. 2The effect of different descending systems on flexor and extensor activity during locomotionBrain Research, Vol. 40, No. 2Ascending and descending excitatory influences in the brain stem reticulum: A re-examinationBrain Research, Vol. 36, No. 2Vestibulospinal Relations: Vestibular Influences on Gamma Motoneurons and Primary AfferentsEffects of hemorrhagic hypotension and shock on the central nervous functionsJournal of Surgical Research, Vol. 10, No. 7The vestibulospinal tract. Effects on alpha-motoneurones in the lumbosacral spinal cord in the catExperimental Brain Research, Vol. 10, No. 1THE ROLE OF NONSPECIFIC RETICULO-THALAMO-CORTICAL SYSTEMS IN EMOTIONThe extrapyramidal systems of the spinal cord. II. Results of combined pyramidal and extrapyramidal lesions in the macaqueThe Journal of Comparative Neurology, Vol. 135, No. 1La Fongtion Vestibulaire Chez L'unau ( Choloepus Hoffmanni Peters )27 September 2008 | Archives Internationales de Physiologie et de Biochimie, Vol. 76, No. 2The alterations of tonus and movements through the interplay between the cerebral hemispheres and the cerebellumThe Journal of Comparative Neurology, Vol. 127, No. S1Effects of prolonged caloric stimulation upon oculomotor, vestibulospinal and segmental spinal activityExperimental Neurology, Vol. 14, No. 3The quick component of nystagmus: A presentation of a theory of its origin and mechanism involving the dynamic rhythmic inhibition of the slow component, based upon a comprehensive review of prior work and additional experimental evidence12 May 2014 | The Laryngoscope, Vol. 75, No. 10Bioelectrical characteristics of regenerated fibers in the feline spinal cordExperimental Neurology, Vol. 2, No. 5THE MODE OF ACTION OF CARISOPRODOL*15 December 2006 | Annals of the New York Academy of Sciences, Vol. 86, No. 1Vestibular influences on spinal mechanismsExperimental Neurology, Vol. 1, No. 3Descending vestibular activity and its modulation by proprioceptive, cerebellar, and reticular influencesExperimental Neurology, Vol. 1, No. 3Elektrische T�tigkeit der Extremit�ten- und Halsmuskulatur bei LabyrinthreizungArchiv f�r Psychiatrie und Nervenkrankheiten, Vol. 197, No. 6The effect of the brain stem reticular formation on the linguomandibular reflexThe Journal of Comparative Neurology, Vol. 102, No. 3Effect of Vestibular Nerve Section Upon the Spinal Influence of the Bulbar Reticular Formation.Acta Physiologica Scandinavica, Vol. 33, No. 2-3The Relation of Oxygen Deprivation to Fetal Reflex Arcs and the Development of Fetal BehaviorThe Journal of Psychology, Vol. 35, No. 1Narcolepsy: A Brief Critical Review and Study of Eight Cases8 February 2018 | Journal of Mental Science, Vol. 98, No. 413Influence of the forebrain on somato-motor activity. II. Facilitation,The Journal of Comparative Neurology, Vol. 94, No. 3Biophysical Aspects of Nervous FunctionProgress in Biophysics and Biophysical Chemistry, Vol. 2Cybernetics as Applied to a Study of Normal and Abnormal Adjustment Mechanisms2 July 2010 | The Journal of Psychology, Vol. 30, No. 1Effects at different frequencies of cerebellar stimulation upon postural tonus and myotatic reflexesElectroencephalography and Clinical Neurophysiology, Vol. 2, No. 1-4 More from this issue > Volume 11Issue 6November 1948Pages 501-507 https://doi.org/10.1152/jn.1948.11.6.501PubMed18894656History Published online 1 November 1948 Published in print 1 November 1948 Metrics

Observations on the gross and microscopic anatomy of the sloths (Bradypus griseus griseus Gray and Choloepus hoffmanni Peters)

AbstractIn this study observations are reported upon the morphological differences between the three‐toed and two‐toed forms of sloths, as well as a comparison made of some aspects between the sloths and the other groups of the Xenarthra. Much attention has been paid to the gross, as well as the histological examination of the viscera, musculature, and the vascular and lymphatic systems.The importance of the correlation of the morphological findings with physiological studies has been emphasized. For example, the probable correlation of the vascular plexuses of the extremities with the postures and muscular activity of the different members of the Xenarthra is discussed. Much new information has been gained concerning the placentation and development of the sloths, as well as concerning the structure of the male and female reproductive tracts.