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Biomedical subjects

W A Spurrier

Publications and source records attributed to W A Spurrier.

18 recordsLinked to original sources
PubMed1990

A circannual cycle in pinealocyte synaptic ribbons in the hibernating and seasonally reproductive 13-lined ground squirrel (Spermophilus tridecemlineatus).

Pinealocyte synaptic ribbons (SR) in the 13-lined ground squirrel were quantified at monthly intervals over a one-year period spanning the hibernating and reproductive cycles of these animals. SR numbers were high (70-90/20,000 microns2) during periods of activity and reproductive quiescence (May-October). With the onset of hibernation (November-December) there was a rapid 6 to 7-fold reduction in SR frequency. During arousal (January-February) and sexual maturation (March-April) there was a gradual increase in SR frequency. The winter decline in SR frequency is consistent with the decline in pineal melatonin during hibernation and supports the hypothesis that pinealocyte SR play an important role in the neurotransduction of melatonin biosynthesis.

Animals↗
PubMed1988

Further studies on opioids and hibernation: delta opioid receptor ligand selectively induced hibernation in summer-active ground squirrels.

To examine the possible involvement of multiple opioid receptors in animal hibernation, we infused opioids selective for mu, kappa, and delta opioid receptors into summer-active ground squirrels (Citellus tridecemlineatus). The effects of those opioid treatments on the hibernation induced by HIT (Hibernation Induction Trigger) were also examined. Mu opioids morphine (1.50 mg/kg/day) and morphiceptin (0.82 mg/kg/day) and kappa opioid peptide dynorphin A (0.82 mg/kg/day) did not induce hibernation. On the contrary, morphine, morphiceptin and dynorphin A antagonized HIT-induced hibernation in summer-active ground squirrels. Infusion of delta opioid DADLE (D-Ala2-D-Leu5 enkephalin; 1.50 mg/kg/day), however, induced summer hibernation in a manner comparable to that induced by HIT. It is concluded therefore that delta opioid receptor and its ligand may be intimately involved in animal hibernation. In view of the fact that HIT was obtained from winter hibernating animals and might therefore be responsible for natural hibernation, our results also suggest that naturally occurring mu and kappa opioids may play an important role in the arousal state of hibernation.

Analgesics↗
PubMed1987

Opioids and hibernation. II. Effects of kappa opioid U69593 on induction of hibernation in summer-active ground squirrels by "hibernation induction trigger" (HIT).

A "Hibernation Induction Trigger" (HIT) isolated from plasma of winter-hibernating woodchucks induced hibernation in summer-active ground squirrels (Citellus tridecemlineatus). Effects of kappa opioid U69593 on the HIT-induced hibernation were examined. U69593 alone did not elicit marked behavioral alteration or hibernation in summer-active ground squirrels. U69593, however, antagonized hibernation induced by HIT in summer active ground squirrels. In the guinea pig ileum myenteric plexus-longitudinal muscle preparation, woodchuck HIT depressed the electrically-induced contraction. The depression was, however, neither reversed nor blocked by naloxone even when naloxone was used at high doses. This study demonstrates that kappa opioid, at least in the case of U69593, was unable to induce hibernation in the summer-active ground squirrels. The results also demonstrate that woodchuck HIT, like the bear HIT, did not act directly at opioid receptors. Together with our previous observation that naloxone blocked summer hibernation induced by HIT (Bruce et al., Life Sci.., this issue), it is tempting to suggest that HIT may not mediate its effects through kappa opioid receptors but may do so through other types of opioid receptors such as mu or delta. U69593 may antagonize HIT-induced hibernation as a mu or delta receptor antagonist.

Animals↗
PubMed1985

Hibernation "trigger" alters renal function in the primate.

Macaque monkeys acclimatized to a restraint chair were fitted with indwelling venous and urinary catheters. After basal rates of urine production and creatinine clearance were determined, a 50 mg dose of plasma dialysate albumin fraction obtained from the woodchuck was administered intravenously in a total volume of 2.5 ml. Plasma fractions were collected during the winter interval of hibernation (hibernation "trigger" or HT), or during the summer active (SAWA) period. Although the SAWA fraction exerted no effects on renal function, HT caused a significant reduction in creatinine clearance. In addition, a tendency toward reduced urine flow and creatinine production occurred following the HT infusion. These findings suggest that over and above the hypothermia, aphagia and opioid-like behavioral depression induced by HT, the albumin fraction (HT) present endogenously in the woodchuck during winter torpor, exerts a direct action on the kidney of the primate, possibly on the mechanisms underlying glomerular filtration and the tubular reabsorption process.

Animals↗
PubMed1982

Hibernation "trigger": opioid-like inhibitory action on brain function of the monkey.

A hibernation "trigger" factor derived from the blood of the hibernating woodchuck acts to suppress vital physiological processes in the primate. When infused into the cerebral ventricle of the conscious monkey, the factor induced hypothermia, behavioral depression, bradycardia and aphagia. The opiate antagonists, naloxone and naltrexone, either reverse or retard these behavioral and physiological signs. We hypothesize that the "trigger" molecule is an endogenous opioid-like peptide which may be unique to the hibernator. Moreover, the non-hibernating primate apparently possesses receptor sites in the brain that are capable of responding to this potent molecule.

Animals↗
PubMed1981

Hibernation "trigger" injected in brain induces hypothermia and hypophagia in the monkey.

In ovariectomized adult female macaque monkeys, cannulae were affixed bilaterally to the skull for intracerbroventricular injection. Baseline temperature, heart rate, food and water intakes were monitored in each animal after it had been acclimatized to a primate restraining chair. Lyophilized serum albumin fractions extracted from the blood of hibernating woodchucks or summer active, nonhibernating woodchucks were reconstituted in an artificial CSF. Following the intracerebroventricular injection of 3.0 to 4.0 mg of hibernating woodchuck albumin (HWA) in a volume of 300 to 400 microliters, a decline in the temperature of the monkey occurred which varied in magnitude and duration. A marked inhibition of food intake, accompanied by a decline in prandial water intake, persisted for 24 to 36 hours. This hypophagia was due mainly to a reduction in the number of feeding episodes during the periods of observation. Although heart rate declined intermittently, respiratory rates remained unchanged. Summer active woodchuck albumin (SAWA) or bovine serum albumin (BSA) given in the identical range of doses, as well as artificial CSF, exerted little or no effect either on body temperature of the primate or on its food intake. These results demonstrate for the first time that a plasma "trigger" factor, obtained from a hibernating animal in torpor, exerts a direct physiological action on the brain of a mammal which is incapable of entering into hibernation. Vital metabolic, thermoregulatory and other control processes mediated by diencephalic and other systems in the CNS are directly suppressed by the "trigger" factor. The clinical implications of these findings are presented.

Animals↗
PubMed1980

A seasonal study of pinealocytes in the 13-lined ground squirrel, Spermophilus tridecemlineatus.

A quantitative histological study of pinealocytes in the 13-lined ground squirrel, Spermophilus tridecemlineatus, was conducted over a period of one year. Consistent and statistically significant seasonal differences were found in nuclear and nucleolar dimensions suggesting a circannual rhythm in the metabolism of these cells. Annual peaks occurred during hibernation, whereas the nadirs occurred during the period of sexual activity. Differences between sexes in any season were not statistically significant. An inverse relationship between nuclear and nucleolar size and the normal sexual cycle suggests that reproduction in this species may be mediated by the pineal gland. The question of what role, if any, the pineal gland plays in hibernation awaits further experimental evidence.

Animals↗
PubMed1979

Hemoglobin alterations of the 13-lined ground squirrel while in various activity states.

1. Characterization of fetal, winter-hibernating, winter-active, summer-active and summer-induced hibernating hemoglobins of 13-lined ground squirrels (Citellus tridecemlineatus) by isoelectric focusing (IEF) pH 7.0-9.0 indicated that this molecule is extremely responsive to the various activity states of this hibernator. 2. Major alterations of ground squirrel hemoglobin occur with the varying activity states as evidenced by the distinctive changes in the isoelectric points (pIs) of these protein components. 3. Hemoglobin from winter-hibernating or summer-induced hibernating ground squirrels does not revert to a fetal type of hemoglobin. 4. The presence of an additional hemoglobin peak pI 6.55 in the summer-induced hibernator may serve as a possible assay for hibernation inducing trigger(s) (HIT) molecules under study in our laboratory.

Animals↗
PubMed1978

Isolation of a hibernation inducing trigger(s) from the plasma of hibernating woodchucks.

Plasma from hibernating woodchucks was desalted utilizing a hollow fiber device having a M. W. cut-off of 5,000. This preparation was fractionated by isoelectric focusing (IEF) in a pH gradient extending from 3.5 to 10.0 resulting in protein components having isoelectric points (pIs) of 4.5, 5.2, 5.5, 6.3, and 7.0. Fraction I (comprised of proteins having pIs of 4.5 and 5.2) induced hibernation within 2 to 6 days in 8 out of 10 summer-active ground squirrels. Fraction II (pI 5.5) and Fraction III (pI 6.3 and 7.0) failed to induce any summer hibernation in 10 animal test groups at identical sample concentrations. Polyacrylamide gel electrophoresis of Fraction I indicated that albumin was a major constituent of this still heterogeneous preparation. Thus, in order to more clearly define the plasma locus of this hibernation inducing trigger(s) (HIT) molecule, whole plasma and/or Fraction I was fractionated by 3 distinct resolving techniques. These included sub-fractionation of Fraction I by isoelectric focusing utilizing a narrower pH gradient extending from 3.5 to 6.0, isotachophoresis of whole plasma and affinity chromatography of Fraction I and whole plasma. A total of 40 summer-active ground squirrels were injected and assayed for HIT activity with fractionated preparations derived by the three previously cited separation techniques. A total of 18 of these summer-active ground squirrels hibernated. However, a much more impressive figure is that 16 out of 21 animals hibernated when injected with resolved hibernating plasma fractions in which albumin was the predominant plasma protein. A total of 8 control animals were injected with vehicle and none of these hibernated.

Animals↗
PubMed1970

Summer hibernation induced by cryogenically preserved blood "trigger".

Summer hibernation induced by transfusions of blood (serum, cells, or whole blood) from hibernating ground squirrels and woodchucks demonstrates that (i) this "trigger effect" can be preserved cryogenically in vitro for at least 5 months, (ii) it cross-reacts between these species of hibernators, and (iii) its effectiveness relates to the donor's previous hibernation history.

Animals↗
PubMed1969

Hibernation induced in ground squirrels by blood transfusion.

Natural mammalian hibernation was continuously maintained under laboratory conditions throughout spring and summer seasons in a colony of thirteen-lined ground squirrels by serial transfusional passage of blood from hibernations animals to active animals. This procedure successfully produced hibernation in animals until late summer, at which time naturally occurring (spontaneous) hibernations occurred in the colony, thus terminating the experiment.

Animals↗