Posterior lymph heart pressure and rate and lymph flow in the toad Bufo marinus in response to hydrated and dehydrated conditions

Posterior lymph heart pressure, rate and flow were measured in chronically cannulated Bufo marinus during normal hydrated and dehydrated conditions. A new surgical technique was developed which allowed direct and constant measurement of the functioning of the posterior lymph hearts with minimal disruption to normal lymph drainage. The mean intra-lymph-heart systolic pressure was 2.29 +/− 0.12 kPa for hydrated animals at rest, decreasing to 1.01 +/− 0.10 kPa after 24 h of dehydration. Similarly, lymph heart rate, which was 48.2 +/− 1.7 beats min-1 under hydrated conditions, decreased to 31.8 +/− 4.6 beats min-1 after 18 h of dehydration. Lymph flow decreased almost to zero during dehydration from a hydrated rate of 1.11 +/− 0.04 ml h-1 100 g-1. This is the first study to measure directly and to correlate these variables in an amphibian and to show specifically that pressure, rate and lymph flow are significantly reduced during periods of dehydration.

Download Full-text

Direct measurement of flow from the posterior lymph hearts of hydrated and dehydrated toads (Bufo marinus).

Journal of Experimental Biology ◽

10.1242/jeb.200.11.1695 ◽

1997 ◽

Vol 200 (11) ◽

pp. 1695-1702 ◽

Cited By ~ 3

Author(s):

J M Jones ◽

A K Gamperl ◽

A P Farrell ◽

D P Toews

Keyword(s):

Heart Rate ◽

Stroke Volume ◽

Systolic Pressure ◽

Lymph Flow ◽

Bufo Marinus ◽

Experimental Chamber ◽

Doppler Flow ◽

Simultaneous Measurements ◽

Pressure Development ◽

Lymph Heart

Flow from the posterior lymph hearts of Bufo marinus was measured using Doppler flow probes. These probes were placed on the posterior vertebral vein and recorded flow as lymph was ejected from the heart. In resting, hydrated toads, mean lymph flow from one of the paired posterior lymph hearts was 25.9 +/- 4.9 ml kg-1 h-1, stroke volume was 8.9 +/- 1.4 microL kg-1 and lymph heart rate was 47.5 +/- 3.7 beats min-1. We estimate that, together, the paired posterior lymph hearts are capable of generating flows that are approximately one-sixtieth of the resting cardiac output. Mean peak systolic pressure developed by the posterior lymph hearts was 1.62 +/- 0.08 kPa. Simultaneous measurements of lymph heart pressure development and flow revealed that the outflow pore of the heart opened at a pressure of 0.71 +/- 0.04 kPa, approximately 113 +/- 5 ms into systole. When toads were moderately disturbed, stroke volume increased by as much as fourfold with little change in lymph heart rate (< 5 beats min-1). When toads were dehydrated, lymph flow decreased by 70% at 12h and by 80% and 24h. Since there was only a modest non-significant decrease in lymph heart rate (30%), this reduction in flow was attributed to decreases in stroke volume (approximately 80%). Lymph heart flow and stroke volume returned to control values 30 min after adding water back into the experimental chamber. Stroke volume was clearly more important in regulating lymph flow than lymph heart rate under these conditions in Bufo marinus.

Download Full-text

Resting Heart Rate of the Toad Bufo marinus: A Long-Term Study of Individual Differences and Environmental Influences

Physiological Zoology ◽

10.1086/physzool.63.2.30158505 ◽

1990 ◽

Vol 63 (2) ◽

pp. 420-431 ◽

Cited By ~ 7

Author(s):

Bryan Dumsday

Keyword(s):

Heart Rate ◽

Individual Differences ◽

Environmental Influences ◽

Bufo Marinus ◽

Resting Heart Rate ◽

Term Study ◽

Long Term Study ◽

Toad Bufo

Download Full-text

Etorphine-halothane anaesthesia in two five-year-old African elephants (Loxodonta africana) : clinical communication

Journal of the South African Veterinary Association ◽

10.4102/jsava.v70i4.789 ◽

1999 ◽

Vol 70 (4) ◽

Cited By ~ 2

Author(s):

G.F. Stegmann

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Systolic Pressure ◽

Loxodonta Africana ◽

African Elephants ◽

Clinical Communication ◽

Dental Surgery ◽

Blood Pressures ◽

The Mean ◽

Mean Heart Rate

Anaesthesia of 2 five-year-old femaleAfrican elephants (Loxodonta africana) was required for dental surgery. The animals were each premedicated with 120 mg of azaperone 60 min before transportation to the hospital. Before offloading, 1 mg etorphine was administered intramuscularly (i.m.) to each elephant to facilitate walking them to the equine induction / recovery room. For induction, 2 mg etorphine was administered i.m. to each animal. Induction was complete within 6 min. Surgical anaesthesia was induced with halothane-in-oxygen after intubation of the trunk. During surgery the mean heart rate was 61 and 45 beats / min respectively. Systolic blood pressures increased to 27.5 and 25.6 kPa respectively, and were treated with intravenous azaperone. Blood pressure decreased thereafter to a mean systolic pressure of 18.1 and 19.8 kPa, respectively. Rectal temperature was 35.6 and 33.9 oC at the onset of surgery, and decreased to 35.3 and 33.5 oC, respectively, at the end of anaesthesia. Etorphine anaesthesia was reversed with 5mg diprenorphine at the completion of 90 min of surgery.

Download Full-text

Lymphatic regulation of hematocrit during hypoxia in the toad Bufo woodhousei

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1995.269.4.r814 ◽

1995 ◽

Vol 269 (4) ◽

pp. R814-R821 ◽

Cited By ~ 9

Author(s):

G. M. Malvin ◽

S. Macias ◽

M. Sanchez ◽

R. Dasalla ◽

A. Park ◽

...

Keyword(s):

Plasma Volume ◽

Lymph Flow ◽

Cholinergic Nerves ◽

Arterial Blood ◽

Rate Of Increase ◽

Lymph Heart ◽

Flow Through ◽

Bufo Woodhousei ◽

Induced Changes ◽

Toad Bufo

Hypoxia rapidly increases hematocrit (Hct) in anuran amphibians by reducing plasma volume, but the mechanism(s) mediating this response is unknown. We tested the hypothesis that, during hypoxia, plasma volume is reduced by impaired lymph heart (LH) function, decreasing lymph flow into the circulation. In Bufo woodhousei, we measured the effects of hypoxia on Hct, lymph heart rate (LHR), LH pressure, the movement of dye from the dorsal lymph sac to the arterial blood, and flow through an open LH cannula. We also tested whether splenic contraction or cholinergic nerves contribute to the hypoxia-induced changes. Graded hypoxia between 21 and 4% O2 produced graded increases in Hct (P < 0.0001) and decreases in LHR (P = 0.01). Hypoxia reduced the rate of increase in arterial Evans blue concentration after injection into the dorsal lymph sac (P = 0.041) and decreased flow through an open LH cannula (P < 0.012). Hypoxia increased Hct and reduced LHR similarly in control, splenectomized, and sham-splenectomized toads. Atropine had no significant effect on Hct and LHR. These results indicate that the LHs play a regulatory role in hypoxia-induced hemoconcentration.

Download Full-text

Effect of hematocrit on behavioral thermoregulation of the toad Bufo marinus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1990.258.4.r848 ◽

1990 ◽

Vol 258 (4) ◽

pp. R848-R851 ◽

Cited By ~ 2

Author(s):

S. C. Wood

Keyword(s):

Thermal Gradient ◽

Bufo Marinus ◽

The Body ◽

Behavioral Thermoregulation ◽

Blood Doping ◽

Cross Sectional ◽

Oxygen Capacity ◽

The Mean ◽

Sectional Analysis ◽

Toad Bufo

This study tested the hypothesis that the oxygen capacity of blood, indexed by hematocrit, affects the body temperature (Tb) selected by toads (Bufo marinus) in a thermal gradient. Anesthetized toads (Brevital sodium; 40 mg/kg im) were fitted with a cloacal thermistor and femoral artery cannula. After recovery, they were placed in a thermal gradient ranging from approximately 10 to 40 degrees C. Tb was measured for 24 h. Then 1-2 ml blood were withdrawn and replaced with an equal volume of either 0.66% saline or packed red cells from donor toads. Selected Tb was measured for the next 24 h. The mean Tb selected by B. marinus (n = 33) was 24.9 degrees C. Cross-sectional analysis showed no correlation between selected Tb and hematocrit. However, each toad rendered anemic showed a reduction of selected Tb (mean = 22.9 degrees C). The degree of Tb reduction was correlated with the hematocrit reduction, (r = 0.86; P = 0.013). Blood doping did not have a significant effect on selected Tb. The reduction of Tb could be adaptive by reducing oxygen consumption.

Download Full-text

Autonomic influences on heart rate and blood pressure in the toad, Bufo marinus, at rest and during exercise

Journal of Experimental Biology ◽

10.1242/jeb.134.1.377 ◽

1988 ◽

Vol 134 (1) ◽

pp. 377-396 ◽

Cited By ~ 4

Author(s):

I. Wahlqvist ◽

G. Campbell

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Plasma Catecholamines ◽

Cardiovascular Responses ◽

Blocking Agent ◽

Additional Treatment ◽

Bufo Marinus ◽

Adrenergic Nerve ◽

Exercise Period ◽

Toad Bufo

Blood pressure (PA) and heart rate (HR) were measured in the conscious, resting toad, Bufo marinus. Treatment with bretylium (an adrenergic neurone blocking agent), alone or in combination with phentolamine and propranolol (adrenoceptor antagonists) did not alter PA or HR significantly. Atropine caused a small but significant increase in HR but had no effect on PA. The experiments indicate a cholinergic cardio-inhibitory tone but give no evidence for an adrenergic pressor tone at rest. Treadmill exercise caused a rapid increase in PA and HR which was sustained throughout the exercise period. This response was partly psychogenic. The concentration of plasma catecholamines increased during exercise and was high enough to affect organs that were included in an extracorporeal blood circuit with the exercising animal. Bretylium treatment revealed an initial hypotension, presumably due to work hyperaemia, followed by a hypertension which was reduced compared to controls. The tachycardia was delayed but HR eventually reached control levels. Additional treatment with phentolamine and propranolol did not further affect the PA response, but significantly reduced the tachycardia reached during exercise. It is concluded that the cardiovascular responses to exercise involve adrenergic nerve fibres causing hypertension and an initial rapid tachycardia. Circulating catecholamines seem to be the major cause of the sustained tachycardia.

Download Full-text

Baroreceptor control of heart rate in the conscious toad Bufo marinus

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1981.241.5.r307 ◽

1981 ◽

Vol 241 (5) ◽

pp. R307-R311

Author(s):

D. G. Smith ◽

P. J. Berger ◽

B. K. Evans

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Mean Arterial Pressure ◽

Arterial Pressure ◽

Bufo Marinus ◽

Carotid Circulation ◽

Normalized Gain ◽

Toad Bufo

Perivascular balloons were used to elicit heart rate (HR) responses to imposed changes in mean arterial pressure (Pa) in conscious unrestrained toads (Bufo marinus). It is clear that functional baroreceptors lie in the pulmocutaneous arteries of B. marinus, and that these can elicit compensatory heart rate responses to perturbations of blood pressure. Functional baroreceptors were not present in the carotid circulation and are probably absent from the lateral aortae and conus arteriosus as well. Normalized gain of the baroreceptor-heart rate reflex (delta HR%/delta Pa) in five toads was 13%/kPa, which is considerably less than that found in other vertebrates to date.

Download Full-text