RESUMO
The first event of cellular differentiation consists of the segregation of the trophectoderm and the inner cell mass. Studies in mice suggest that cell contractility and the formation of an apical domain play important roles in this event; however, this remains unknown in the bovine. We tested the hypothesis that blocking apical domain formation would halt subsequent trophectoderm differentiation in bovine embryos. We first assessed the formation of an apical domain by the presence of Par-6 Family Cell Polarity Regulator Beta (PARD6B) and Ezrin (EZR), which appeared after the 8-cell stage. We inhibited apical domain formation by blocking cell contractility with 25µM (-)-blebbistatin. Treatment from 90 to 186h after insemination did not reduce blastocyst development compared with the untreated control group or the group treated with inactive (+)-blebbistatin. Immunofluorescence staining after blebbistatin treatment revealed the absence of EZR and the trophectoderm marker Caudal Type Homeobox 2 (CDX2). Following blebbistatin treatment, Yes1 Associated Transcriptional Regulator (YAP), which is involved in the Hippo signalling pathway, exhibited cytoplasmic staining instead of nuclear localisation. Despite changes in protein expression and localisation, no difference in trophectoderm or total cell numbers was observed. In conclusion, inhibition of cell contractility inhibited apical domain formation without impairing blastocyst formation, suggesting that a different biological mechanism is involved in trophectoderm and inner cell mass differentiation in bovine embryos.
RESUMO
Antibiotic and nonpreference mechanisms are related in cucumber through the action of the bi gene and the absence of cucurbitacins. Cucurbitacins attract cucumber beetles and cause feeding whereas they have an antibiotic effect on two-spotted mites.
RESUMO
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.
Assuntos
Eletrocardiografia/veterinária , Frequência Cardíaca/fisiologia , Bichos-Preguiça/fisiologia , Animais , Humanos , Masculino , PosturaRESUMO
Studies on acetyl phosphate (AcP2-), one of the so-called 'energy-rich' mixed-acid anhydrides, are summarized. Based on stability constants determined by potentiometric pH titrations in aqueous solution, it is shown that the M(AcP) complexes of Ca2+, Mg2+, Mn2+, Cu2+, and Zn2+ are more stable than is expected from the basicity of the phosphate group of AcP2-. This observed stability increase is attributed to an additional interaction of the already phosphate-coordinated metal ion (M2+) with the carbonyl oxygen of the anhydride unit. These conclusions are corroborated by the properties of the complexes of the hydrolysis-stable acetonylphosphonate (AnP2-). The formation degrees of the various six-membered chelates occurring in the M(AcP) and M(AnP) systems are presented and evidence is given that these chelates persist in mixed ligand complexes and that their formation degree is promoted by a low solvent polarity. The biological relevance of these results regarding carbonyl oxygen-metal ion interactions is briefly indicated.
Assuntos
Anidridos/química , Cátions Bivalentes/química , Organofosfatos/química , Cálcio/química , Cobre/química , Estabilidade de Medicamentos , Concentração de Íons de Hidrogênio , Cinética , Ligantes , Magnésio/química , Manganês/química , Modelos Químicos , Conformação Molecular , Potenciometria , Zinco/químicaRESUMO
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.
Assuntos
Bichos-Preguiça/fisiologia , Anestesia/veterinária , Animais , Comportamento Animal , Encéfalo/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Feminino , Humanos , Rim/fisiologia , Masculino , Reprodução/fisiologia , Fenômenos Fisiológicos Respiratórios , Sono/fisiologia , Bichos-Preguiça/sangue , Medula Espinal/fisiologia , Visão Ocular/fisiologiaRESUMO
This is a review of the research undertaken since 1971 on the behavior and physiological ecology of sloths. The animals exhibit numerous fascinating features. Sloth hair is extremely specialized for a wet tropical environment and contains symbiotic algae. Activity shows circadian and seasonal variation. Nutrients derived from the food, particularly in Bradypus, only barely match the requirements for energy expenditure. Sloths are hosts to a fascinating array of commensal and parasitic arthropods and are carriers of various arthropod-borne viruses. Sloths are known reservoirs of the flagellate protozoan which causes leishmaniasis in humans, and may also carry trypanosomes and the protozoan Pneumocystis carinii.
Assuntos
Arbovírus/fisiologia , Artrópodes/fisiologia , Comportamento Animal/fisiologia , Vetores de Doenças , Bichos-Preguiça/fisiologia , Fenômenos Fisiológicos da Nutrição Animal , Animais , Arbovírus/isolamento & purificação , Digestão/fisiologia , Fenômenos Fisiológicos do Sistema Digestório , Ecologia , Eucariotos/isolamento & purificação , Feminino , Cabelo/química , Cabelo/fisiologia , Masculino , Bichos-Preguiça/parasitologia , Bichos-Preguiça/virologiaRESUMO
The aim of the present study was to confirm whether feeding influences the resting breathing rate and to observe possible alterations in blood gas and pH levels produced by feeding in unanesthetized sloths (Bradypus variegatus). Five adult male sloths (4.1 +/- 0.6 kg) were placed daily in an experimental chair for a period of at least 4 h for sitting adaptation. Five measurements were made for each sloth. However, the sloths one, two and five were studied once and the sloths three and four were studied twice. Breathing rate was determined with an impedance meter and the output signal was digitized. Arterial blood samples were collected for blood gas analysis with a BGE electrolytes analyzer and adjusted for the animal's body temperature and hemoglobin content. The data are reported as mean +/- SD and were collected during the resting period (8:00-10:00 h) and during the feeding period (16:00-18:00 h). The mean breathing rate increased during mastication of ymbahuba leaves (rest: 5.0 +/- 1, feeding: 10 +/- 1 bpm). No significant alterations were observed in arterial pH (rest: 7.42 +/- 0.05, feeding: 7.45 +/- 0.03), PCO2 (rest: 35.2 +/- 5.3, feeding: 33.3 +/- 4.4 mmHg) or PO2 (rest: 77.5 +/- 8.2, feeding: 78.4 +/- 5.2 mmHg) levels. These results indicate that in unanesthetized sloths 1) feeding evokes an increase in breathing rate without a significant change in arterial pH, PCO2 or PO2 levels, and 2) the increase in breathing rate produced by feeding probably is due to the act of mastication.
Assuntos
Ingestão de Alimentos/fisiologia , Respiração , Bichos-Preguiça/fisiologia , Animais , Gasometria , Testes Respiratórios , Dióxido de Carbono/análise , Ácido Carbônico/análise , Comportamento Alimentar , Concentração de Íons de Hidrogênio , Masculino , Bichos-Preguiça/sangueRESUMO
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.
Assuntos
Pressão Sanguínea/fisiologia , Ritmo Circadiano/fisiologia , Bichos-Preguiça/fisiologia , Análise de Variância , Animais , Feminino , Frequência Cardíaca/fisiologia , Masculino , Telemetria/métodosRESUMO
Heart rate (HR) and systolic (SBP), diastolic (DBP) and mean (MBP) blood pressure were recorded by biotelemetry in nine conscious unrestrained sloths for 1 min every 15 min over a 24-h period. The animals were allowed to freely move in an acoustically isolated and temperature-controlled (24 +/- 1 degree C) experimental room with light-dark cycle (12/12 h). Behavior was closely monitored through a unidirectional visor and classified as resting (sitting or suspended), feeding (chewing and swallowing embauba leaves, Cecropia adenops), or locomotor activity around the tree trunk or on the room floor. Locomotor activity caused statistically significant increases in SBP (+8%, from 121 +/- 22 to 131 +/- 18 mmHg), DBP (+7%, from 86 +/- 17 to 92 +/- 10 mmHg), MBP (+8%, from 97 +/- 19 to 105 +/- 12 mmHg), and HR (+14%, from 84 +/- 15 to 96 +/- 15 bpm) compared to resting values, indicating a possible major influence of the autonomic nervous system on the modulation of cardiac function during this behavior. During feeding, the increase in blood pressure was even higher (SBP +27%, from 119 +/- 21 to 151 +/- 21 mmHg; DBP +21%, from 85 +/- 16 to 103 +/- 15 mmHg; MBP +24%, from 96 +/- 17 to 119 +/- 17 mmHg), while HR remained at 14% (from 84 +/- 15 to 96 +/- 10 bpm) above resting values. The proportionally greater increase in blood pressure than in HR during feeding suggests an increase in peripheral vascular resistance as part of the overall response to this behavior.
Assuntos
Pressão Sanguínea/fisiologia , Ingestão de Alimentos/fisiologia , Frequência Cardíaca/fisiologia , Atividade Motora/fisiologia , Bichos-Preguiça/fisiologia , Animais , Velocidade do Fluxo Sanguíneo/fisiologia , Feminino , Masculino , Descanso/fisiologia , Telemetria/métodosAssuntos
Velocidade do Fluxo Sanguíneo , Resistência Vascular , Animais , Circulação Sanguínea , Cães , Eletrônica Médica , Hematócrito , TemperaturaRESUMO
The aim of this study was to elucidate the role of the baroreflex in blood pressure control in sloths, Bradypus variegatus, since these animals show labile levels in this parameter. Unanesthetized cannulated sloths were positioned in an experimental chair and the arterial catheter was coupled to a strain gauge pressure transducer. Blood pressure was monitored before, during and after the administration of phenylephrine (0.0625 to 4 microg/kg) and sodium nitroprusside (0.0625 to 2 microg/kg), bringing about changes in mean blood pressure from +/-30 mmHg in relation to control values. The relation between heart rate changes due to blood pressure variation was estimated by linear regression analysis. The slope was considered the reflex baroreceptor gain. The results (means+/-SD) showed that the reflex baroreceptor gain was -0.3+/-0.1 bpm/mmHg (r=0.88) to phenylephrine and -0.5+/-0.1 bpm/mmHg (r=0.92) to sodium nitroprusside, denoting a reduced reflex baroreceptor gain when compared with other mammals, suggesting that in sloths the baroreceptors are minimally involved in the buffering reflex response to these drugs. These findings suggest that the labile blood pressure could be influenced or be a result of this lowering in the reflex baroreceptor gain.
Assuntos
Pressão Sanguínea/fisiologia , Bichos-Preguiça/fisiologia , Anestesia , Animais , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Nitroprussiato/farmacologia , Fenilefrina/farmacologia , Pressorreceptores/metabolismo , Análise de Regressão , Fatores de TempoRESUMO
The stability constants of the 1:1 complexes formed between Pb2+ and the nucleosides (Ns), adenosine and guanosine, as well as between the nucleotides (NMP2-), AMP2-, IMP2-, and GMP2-, were determined by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.1 M, NaNO3). Based on previously established log KPb(R-PO3)Pb versus pKH(R-PO3)H straight-line plots (R-PO3(2-) = simple phosphate monoester or phosphonate ligands where R is a noninteracting site), it is shown that the Pb(IMP) and Pb(GMP) complexes are more stable than is expected on the basis of the basicity of the phosphate group of IMP2- and GMP2-. This means that macrochelates are formed, where the phosphate-coordinated Pb2+ also interacts with N7 of the nucleobase residue. In contrast, the stability of the Pb(AMP) complex is governed by the basicity of the AMP2- phosphate group. These results agree with the observations made for the Pb(Ns)2+ complexes: Pb(adenosine)2+ is very unstable in contrast to Pb(guanosine)2+, the stability of which is very similar to the one of Pb(cytidine)2+ studied previously. The stability constants of the Pb(Ns)2+ complexes also allowed an evaluation of the structure in solution of the monoprotonated Pb(H;NMP)+ complexes, the stabilities of which were also determined. We were able to show that the proton is located at the phosphate group and Pb2+ at the N7/(C6)O site of H(GMP)-; in the case of H(AMP)- Pb2+ is probably about equally distributed between the adenine residue and the monoprotonated phosphate group. On the basis of the stability constants of these complexes and their structures in solution, it is possible to provide a series which reflects the decreasing affinity for Pb2+ of nucleobase residues in single-stranded nucleic acids: guanine approximately equal to cytosine > (hypoxanthine) > adenine > uracil approximately equal to thymine. The Pb2+ affinity of the phosphodiester linkage, -PO3(-)-, is similar to the one of the adenine residue, but is expected to be more significant due to its larger abundance. The relevance of these results for lead-activated ribozymes is briefly discussed.
Assuntos
Monofosfato de Adenosina/química , Guanosina Monofosfato/química , Inosina Monofosfato/química , Chumbo/química , Concentração de Íons de Hidrogênio , Cinética , Modelos Moleculares , Estrutura Molecular , Soluções , ÁguaRESUMO
The stability constants of the 1:1 complexes formed between Pb2+ and several simple phosphate monoesters (4-nitrophenyl phosphate, phenyl phosphate, D-ribose 5-monophosphate, n-butyl phosphate) or phosphonate ligands (methylphosphonate, ethylphosphonate) (R-PO3(2-)) were determined by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.1 M, NaNO3). The construction of a logK(Pb)Pb(R-PO3) versus pK(H)H(R-PO3) plot for the mentioned ligand systems results in a straight line on which the data pairs (the corresponding equilibrium constants were also measured) for uridine 5'-monophosphate (UMP2-) and thymidine 5'-monophosphate (dTMP2-) also fall; this result shows that in the Pb2+ complexes of UMP2-and dTMP2- the nucleobase residues do not interfere, in neither a positive nor a negative way, with the binding of Pb2+ and that the stability of all these complexes is determined by the basicity of the phosph(on)ate group. The mentioned straight-line correlation (as defined by the least-squares procedure) allowed us to demonstrate (via constants determined now) that the stability of the Pb2+ complex of cytidine 5'-monophosphate (CMP2-) is also solely determined by the basicity of its phosphate group. A similar evaluation, based on literature data, for the Pb(HPO4) complex reveals that its stability corresponds closely to the expectations based on the Pb(R-PO3) data, though there is a slight hint that Pb(HPO4) may be somewhat more stable [which would be in agreement with previous observations of other M(HPO4) complexes]; clearly, more such comparisons are possible with the reference line given now. Based on the stability constants of the monoprotonated Pb(H;CMP)+ complex and the Pb(cytidine)2+ species (which was also measured now), it is concluded that in Pb(H;CMP)+ the proton is located at the phosphate group and Pb2+ mainly at the N3/(C2)O site of the cytosine residue. Regarding nucleic acids in solution, it is further concluded that the affinity of Pb2+ towards the negatively mono-charged phosphate unit, -O--P(O)2- -O-, of a nucleic acid backbone is comparable to that of the cytosine moiety, the affinity towards other nucleobase residues being smaller. This information may prove helpful regarding the properties of lead ribozymes.
Assuntos
Monofosfato de Citidina/química , Chumbo/química , Timidina Monofosfato/química , Uridina Monofosfato/química , Ésteres/química , Ligantes , Organofosfonatos/química , Relação Estrutura-AtividadeRESUMO
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.
Assuntos
Estimulação Elétrica , Eletrocardiografia , Bichos-Preguiça/fisiologia , Fibrilação Ventricular/fisiopatologia , Xenarthra/fisiologia , Animais , Temperatura Corporal , Peso Corporal , Cães , Feminino , Coração/anatomia & histologia , Masculino , Tamanho do Órgão , Bichos-Preguiça/anatomia & histologiaRESUMO
Buckwheat (Fagopyrum esculentum, Moench), a herbaceous plant of the Polygonaceae family, does not have any affinity for the Gramineae family. It is commercially rated as a cereal, which has led to some misunderstanding concerning its use in gluten induced enteropathy or celiac disease. The effect of buckwheat flour ingestion by celiac patients was evaluated through the indirect immunofluorescence technique. Samples of serum were collected 30 days after the flour ingestion. Cryostat performed cuts of wheat and buckwheat grains were accomplished in order to compare the reactivity of their proteins and serum of celiac and normal patients. The assay revealed that the buckwheat flour presents no toxicity for the celiac patient and no anti-protein antibodies formation in the grain was observed for serum dilutions of 1:2 up to 1:32 with 0.15 M NaCl solution in 0.01 M phosphate buffer, pH 7.2 throughout the 30 day assay period. The results of the immunological assays showed that the buckwheat flour does not present toxic prolamines to celiac disease patients.
Assuntos
Doença Celíaca/imunologia , Grão Comestível/imunologia , Glutens/imunologia , Anticorpos/sangue , Estudos de Casos e Controles , Doença Celíaca/sangue , Criança , Imunofluorescência , Gliadina/sangue , Gliadina/imunologia , HumanosRESUMO
1. Chloralose, 50 mg/kg i.v., is a safe effective anesthetic for sloths and reduces incidence of cardiac arrhythmias. 2. However, chloralose blocks baroreflexes and may reduce the sensitivity of beta 1 cardiac receptors. 3. Reserpine, 0.70 mg/kg given i.v. in divided doses, blocks the hypertensive effect of 100 micrograms/kg of tyramine in sloths. 4. Reserpine in this dosage materially reduces arterial pressure and heart rate; these effects last at least 7 days. 5. Reserpine potentiates the hypertensive effects of epinephrine and norepinephrine materially. 6. In sloths reserpine increases cardiac irritability but does not block baroreflexes. 7. As is true with most other drugs sloths are more sensitive to chloralose and reserpine than most common laboratory animals.
Assuntos
Cloralose/farmacologia , Reserpina/farmacologia , Bichos-Preguiça , Xenarthra , Animais , Pressão Sanguínea/efeitos dos fármacos , Epinefrina/farmacologia , Isoproterenol/farmacologia , Norepinefrina/farmacologiaRESUMO
1. Tilting sloths anesthetized with chloralose from erect to supine or supine to erect produced little or no effect on heart rate. 2. Tilting anesthetized sloths from erect to supine increased both systolic and diastolic pressures significantly and by about the same amounts. The maximum effect was produced in 20 sec. 3. Pressures stabilized at a higher level than in the erect posture but below the maximum reached in tilting. 4. Tilting these sloths from the supine to the erect posture resulted in a rapid (20 sec) and dramatic fall in pressures to below the initial erect pressure levels. Return to initial erect levels took place slowly. 5. Tilting reserpinized sloths from erect to supine or supine to erect produced little or no effect on heart rate. 6. Tilting reserpinized sloths from erect to supine increased both systolic and diastolic pressures materially and by similar amounts. The maximum effect took 50 sec. 7. Pressures stabilized at higher levels than in the erect posture but less than maximum reached with tilting. 8. Tilting these sloths from supine to erect caused significant falls in pressure to slightly below the initial erect pressure, with maximum effect reached in 30 sec and eventual return to control level. 9. Pressure changes were almost entirely the result of altered venous return. 10. Neither chloralose nor reserpine completely blocked vascular control but reduced it materially.
Assuntos
Anestesia , Pressão Sanguínea/fisiologia , Frequência Cardíaca/fisiologia , Postura/fisiologia , Reserpina/farmacologia , Bichos-Preguiça/fisiologia , Xenarthra/fisiologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Cloralose , Frequência Cardíaca/efeitos dos fármacosRESUMO
1. In unanesthetized, minimally restrained three-toed sloths, Bradypus tridactylus, the mean arterial pressure was 125/85 mmHg and the heart rate was 83.6 beats/min. There was no significant difference between these parameters whether the animal was erect or supine in the experimental chair. 2. Animals without any restraint had a mean blood pressure of 133/87 mmHg and a heart rate of 78.1 beats/min. There was no significant difference between these parameters whether the animal was seated or suspended from a horizontal bar and there was no significant difference between the minimally restrained and the unrestrained animals. 3. Tilting from the erect to the supine position produced large increases in blood pressure parameters, 37% in systolic and 21% in diastolic, reaching the maximum effect in a mean time of 38 sec. Tilting from the supine to the erect position caused even greater increases in pressure, 43% and 38% respectively, and reaching the maximum also in a mean time of 38 sec. 4. Tilting initially increased the heart rate, in going from erect to supine by 21% in 16 sec and from supine to erect by 23% in 20 sec. 5. In going from erect to supine there was a reflex bradycardia later, 15% below control level with a maximum at 40 sec, and to a lesser degree in going from supine to erect, 9% with maximum at 50 sec.
Assuntos
Pressão Sanguínea , Frequência Cardíaca , Bichos-Preguiça/fisiologia , Xenarthra/fisiologia , Animais , Estado de Consciência , Feminino , Masculino , PosturaRESUMO
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.
Assuntos
Pressão Sanguínea , Frequência Cardíaca , Postura , Bichos-Preguiça/fisiologia , Xenarthra/fisiologia , Animais , Atropina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Interações Medicamentosas , Frequência Cardíaca/efeitos dos fármacos , Propranolol/farmacologiaRESUMO
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.