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Biomedical subjects

V H Hutchison

Publications and source records attributed to V H Hutchison.

At least 19 recordsLinked to original sources
PubMed1992

Influence of temperature and photoperiod on plasma melatonin in the mudpuppy, Necturus maculosus.

A melatonin (MEL) radioimmunoassay employed previously only in mammals was used to estimate plasma MEL in a salamander, Necturus maculosus. Validation procedures included thin-layer chromatography of plasma extracts, parallel inhibition curves of authentic MEL and serially diluted plasma and plasma extracts and quantitative recovery of authentic MEL added to pooled Necturus plasma. A diel cycle of plasma MEL was demonstrated in mudpuppies acclimatized for a minimum of 3 weeks under a 12L:12D photoperiod and 15 +/- 1 degrees and sampled in late March. The MEL cycle persisted under a reversed photoperiod (lights on, 1800 hr), but the amplitude of the MEL peak was diminished, and the peak was more than 180 degrees out of phase with the corresponding peak under a normal photoperiod. In animals acclimated to 5 degrees in mid-June under a 12L:12D photoperiod, the diel cycle of plasma MEL continued, but both midphotophase and midscotophase concentrations were reduced compared with 15 degrees controls. The diel cycle was also present in animals acclimated to 25 degrees, but the decrease in MEL concentrations was less marked than that in 5 degrees animals. Photoperiod is apparently the primary cue for cycles in plasma MEL in Necturus, but the cycle can be influenced by temperature.

Animals↗
PubMed1987

Blood changes in Bufo cognatus following acute heat stress.

1. Various blood constituents were measured in an attempt to identify the effects of exposure of Great Plains toads to the critical thermal maximum (CTmax) and determine the time course of the onset of and recovery from these effects. 2. Tests for generalized tissue damage including serum glutamic-oxalacetic and glutamic-pyruvic transaminases (SGOT, SGPT), total protein and blood urea nitrogen (BUN) were unaffected by acute thermal stress. 3. Hematocrit, erythrocyte number, mean cell volume and hemoglobin concentration were also unchanged. 4. Blood glucose, lactic acid and creatine phosphokinase (CPK) levels all increased significantly. 5. Blood pH, PO2 and [HCO3-] also increased with acute heat stress while PCO2 decreased. 6. Long-term exposure to temperatures near the CTmax may cause severe tissue damage. Acute thermal stress does not appear to cause damage other than the short-term, reversible effects of strong physical exercise.

Acclimatization↗
PubMed1986

Histamine and histamine receptors: behavioral thermoregulation in the salamander Necturus maculosus.

Low doses (0.01, 0.1 mg/kg, i.p.) of histamine (HA) caused selection of significantly lower temperatures, and higher doses (0.5, 1.0 mg/kg) increased temperatures by mudpuppies in linear thermal gradients. Injection of the HA precursor, L-histidine (500 mg/kg) produced an increase in the temperatures selected. Results from injections of HA H1-receptor agonist (2-pyridylethylamine) and antagonist (pyrilamine), and H2-receptor agonist (dimaprit) and antagonist (cimetidine) had significant effects on thermoregulation; H1-receptors may mediate behavioral hyperthermia and H2-receptors behavioral hypothermia. Responses to these histaminic compounds are significantly influenced by the time of day at which the responses are measured and by season and acclimation temperature. The equivalent behavioral responses in both endotherms and ectotherms to agents which produce physiological hyperthermia and hypothermia are probably behavioral hypothermia ("cold seeking") and behavioral hyperthermia ("heat seeking"), respectively.

Animals↗
PubMed1985

Oxygen transfer characteristics of the blood of reedfish, Erpetoichthys calabaricus.

Oxygen transport characteristics and phosphate compounds were measured in the blood of reedfish, Erpetoichthys calabaricus, a bimodal breather. Blood from reedfish possessed the following values (mean +/- SD): hematocrit (21.7 +/- 0.4%), hemoglobin concentration (7.53 +/- 1.75 g%), red blood cell count (0.45 +/- 0.10 X 10(6)/mm3) and oxygen capacity (10.1 +/- 2.3 vol%). Although hematocrit, hemoglobin concentration, red blood cell count and oxygen capacity were all highly intercorrelated (P less than 0.01 in all cases), none of these parameters were significantly correlated with sex, weight or length in our sixteen fish sample. Erythrocyte volumes equalled 480 micrometers3, showed less variation (CV = 10.4%) and did not correlate with any other measured variable. Blood oxygen dissociation curves were sigmoidal and the P50's equalled 17.34 +/- 3.04 at 1% CO2 and 25 degrees C. Mean Bohr shift (delta log P50/delta pH) was -0.274 +/- 0.087. Temperature strongly influenced blood oxygen affinity. At 1% CO2, delta log P50/delta T equalled 0.026 +/- 0.006 (mean +/- SD). These hematological properties indicate that the blood of reedfish is similar to those of other tropical air-breathering species. Concentrations of total phosphate in the erythrocytes and percentage of total phosphate bound as nucleotide triphosphates were high. Surprisingly, 2,3diphosphoglycerate was found which has been reported in the erythrocytes of only two other fish species. Blood characteristics of reedfish exposed to air for 4 hr with one exception (Hill numbers) were not significantly different from water exposed controls. This suggests that the reedfish does not possess blood respiratory mechanisms to facilitate respiration solely by air-breathing.

Animals↗
PubMed1984

Erythrocytic organic phosphates: diel and seasonal cycles in the frog, Rana berlandieri.

Hemoglobin (Hb) concentration, hematocrit (Hct), total organic phosphates (Ptot), nucleoside triphosphates (NTP), 2,3-diphosphoglycerate (DPG), and "inositol polyphosphates" (IPP) were measured in the erythrocytes of adult frogs at different times of day in winter and summer after acclimatization to 15 degrees C and an LD 12:12 photoperiod. The same measurements were also made on animals acclimated to LD 16:8 in summer. All of the measured parameters varied significantly at different times of the day and between seasons in animals acclimated to an LD 12:12 photoperiod. Summer animals acclimated to LD 16:8 showed significant diel cycles only in Hct and Hb.

2,3-Diphosphoglycerate↗
PubMed1984

Decreased thermal tolerance in Mus musculus with melatonin and chlorpromazine.

Adult Mus musculus, previously acclimatized for two weeks to 25 degrees C and an LD 12:12 photoperiod, were injected (i.p.) with daily doses of melatonin (4.0 mg) or chlorpromazine (20.0 mg kg-1) for 2 days. Both drugs significantly reduced the critical thermal maximum (CTM) and the elevated defended temperature (EDT). Melatonin significantly increased the length of EDT but chlorpromazine had no effect on EDT. Both drugs reduce thermal tolerance in ectotherms, but this is apparently the first demonstration that melatonin and chlorpromazine increase sensitivity to high temperature in an endotherm.

Adaptation, Physiological↗
PubMed1979

Aerobic and anaerobic contributions to sustained activity in Xenopus laevis.

In conditions of declining water PO2, Xenopus obtains the majority of resting oxygen needs from lung breathing at 15 degrees and 25 degrees C. The critical oxygen tension was 120 +/- 9 mm Hg at 15 degrees C, and 90 +/- 10 mm Hg at 25 degrees C. During 30 min stimulation of activity to complete exhaustion at 15 degrees C, frogs exhibited an aerobic capacity of 1.7 microliter O2.g-1.h-1 and accumulated 2.22 mg lactate . g-1. Following activity these animals exhibited an oxygen debt of 49.2 microliter O2.g-1. At 25 degrees C, Xenopus had an aerobic capacity of 16.1 microliter O2.g-1 and accumulated 1.94 mg lactate . g-1. Following activity, 25 degrees C frogs exhibited an oxygen debt of 261.9 microliter O2.g-1. Thus at 15 degrees C, Xenopus acquires 85% of the ATP used during a bout of sustained exhaustive activity from anaerobic sources, and 98% at 25 degrees C. Recovery from exhaustive activity was complete after 5 h at 25 degrees C and 9 h at 15 degrees C. Comparison of these data with those of other amphibians stimulated to sustained activity suggests that aquatic amphibians can tolerate a larger lactate load than can terrestrial forms.

Animals↗
PubMed1976

Parietalectomy and thermal selection in the lizard Sceloporus magister.

Lizards were acclimatized to various regimes of temperature (15 degrees, 35 degrees C) and photoperiod (LD 08:16, 16:8). Parietalectomized, sham operated, and control animals were placed in thermal gradients and their body temperatures monitored for periods of up to 15 days. Daily rhythms of thermal selection were evident with higher temperatures selected in late photophase and lower temperatures selected in scotophase. Thermal selection was more variable in scotophase than in photophase. Parietalectomized lizards chose significantly higher body temperatures than did shams or controls. Acclimatization to temperature and photoperiod had little or no effect on the thermal preferendum. The preferred body temperature of controls was 33.2 degrees C +/- 3.59. Length of time in the gradient tended to change thermal preference, especially in lizards acclimated to 15 degrees C. Through interactions with the pineal gland the parietal eye is probably important in synchronizing many bodily functions with photoperiod.

Acclimatization↗
PubMed1976

Aquatic life at high altitude: respiratory adaptations in the Lake Titicaca frog, Telmatobius culeus.

Telmatobius culeus has a combination of behavioral, morphological and physiological adaptations which allows an aquatic life in cool (10 degrees C) O2-saturated (at 100 mm Hg) waters at high altitude (3812 m). The skin surgace area is increased by pronounced folds and the cutaneous capillaries penetrate to the outer layers of the skin. The erythrocyte volume (394 mu3) is the smallest reported for amphibians. The P50 (15.6 at ph 7.65 and 10 degrees C) is the lowest, and the erythrocyte count (729 - 103/mm3) the highest for an anuran. The O2 capacity (11.7 vol%), hemoglobin (8.1 g/100 ml), hemoglobin concentration (0.281 pg/mu3) and hematocrit (27.9%) measured at 18 degrees C and 3800 m are all elevated in comparison with most amphibians. The O2 dissociation curve is sigmoid (n = 2), the Bohr factor is small (deltalog P50/deltapH = -0.30) and the buffering capacity (-8.9 m M HCO3 - 1-1) is typical for an aquatic amphibian. The metabolic rate (14.1 mul -g-1-h-u) is the lowest reported for a frog and among amphibians only the giant salamanders (Amphiuma, Necturus and Siren) have lower values. If prevent from surfacing in hypoxic waters, the frogs ventilate the skin by "bobbing" behavior; if allowed to surface, they will ventilate the small lungs and the metabolic rate increases to 23 mul-g-1-h-1.

Adaptation, Physiological↗