Flight muscle and heart phenotypes in the high-flying ruddy shelduck.

Ruddy shelduck migrate from wintering grounds in lowland India and Myanmar to breeding grounds in central China and Mongolia, sustaining flight over the Himalayas, where oxygen availability is greatly reduced. We compared phenotypes of the pectoralis muscle and the ventricle of the heart from ruddy shelduck and common shelduck (a closely related low-altitude congener) that were raised in common conditions at sea level, predicting that oxidative capacity would be greater in ruddy shelduck to support high-altitude migration. Fibre-type composition of the pectoralis and the maximal activity of eight enzymes involved in mitochondrial energy metabolism in the pectoralis and heart, were compared between species. Few differences distinguished ruddy shelduck from common shelduck in the flight muscle, with the exception that ruddy shelduck had higher activities of complex II and higher ratios of complex IV (cytochrome c oxidase) and complex II when expressed relative to citrate synthase activity. There were no species differences in fibre-type composition, so these changes in enzyme activity may reflect an evolved modification in the functional properties of muscle mitochondria, potentially influencing mitochondrial respiratory capacity and/or oxygen affinity. Ruddy shelduck also had higher lactate dehydrogenase activity concurrent with lower pyruvate kinase and hexokinase activity in the left ventricle, which likely reflects an increased capacity for lactate oxidation by the heart. We conclude that changes in pathways of mitochondrial energy metabolism in the muscle and heart may contribute to the ability of ruddy shelduck to fly at high altitude.

Age-related increase in mitochondrial quantity may mitigate a decline in mitochondrial quality in red blood cells from zebra finches (Taeniopygia guttata).

Aging is typically associated with a decline in whole animal performance that ultimately contributes to death. It is suspected that a decline in ATP production leads to dysfunction in cellular processes, contributing to the decline in performance. Birds require large amounts of ATP to support physiological process, especially flight, which is one of the most energetically expensive forms of locomotion in the animal kingdom to sustain. Since the bulk of ATP production is coordinated through mitochondrial activity, we set out to explore mitochondrial function in young (~8 months) and old (~73 months) zebra finches (Taeniopygia guttata). We exploited the fact that avian red blood cells (RBCs) are nucleated and have functional mitochondria to explore the phenomenon of age-related decline in mitochondrial function without the need for terminal sampling. We found that RBCs from old zebra finches have lower flux control ratios (mitochondrial O2 consumption attributed to ATP production; 0.29-0.36-fold), exhibit higher respiration (1.4-fold), and significantly higher citrate synthase activity (1.4-fold) than young birds. Respiration rates normalized to citrate synthase activity suggest that mitochondrial quality is changing, as leak state is significantly lower (0.39-fold) in old zebra finches in comparison to young animals. Overall, our findings indicate a possible change in the function of mitochondria in older zebra finches, which may be associated with a corresponding increase in mitochondrial quantity, possibly to offset a decline in mitochondrial quality.

Effects of chronic hypoxia on diaphragm function in deer mice native to high altitude.

AIM: We examined the effects of chronic hypoxia on diaphragm function in high- and low-altitude populations of Peromyscus mice. METHODS: Deer mice (P. maniculatus) native to high altitude and congeneric mice native to low altitude (P. leucopus) were born and raised in captivity to adulthood and were acclimated to normoxia or hypobaric hypoxia (12 or 9 kPa, simulating hypoxia at 4300 and 7000 m) for 6-8 weeks. We then measured indices of mitochondrial respiration capacity, force production, and fatigue resistance in the diaphragm. RESULTS: Mitochondrial respiratory capacities (assessed using permeabilized fibres with single or multiple inputs to the electron transport system), citrate synthase activity (a marker of mitochondrial volume), twitch force production, and muscle fatigue resistance increased after exposure to chronic hypoxia in both populations. These changes were not well explained by variation in the fibre-type composition of the muscle. However, there were several differences in diaphragm function in high-altitude mice compared to low-altitude mice. Exposure to a deeper level of hypoxia (9 kPa vs 12 kPa) was needed to elicit increases in mitochondrial respiration rates in highlanders. Chronic hypoxia did not increase the emission of reactive oxygen species from permeabilized fibres in highlanders, in contrast to the pronounced increases that occurred in lowlanders. In general, the diaphragm of high-altitude mice had greater capillary length densities, produced less force in response to stimulation and had shorter relaxation times. The latter was associated with higher activity of sarcoplasmic reticulum Ca2+ -ATPase (SERCA) activity in the diaphragm of high-altitude mice. CONCLUSION: Overall, our work suggests that exposure to chronic hypoxia increases the capacities for mitochondrial respiration, force production and fatigue resistance of the diaphragm. However, many of these effects are opposed by evolved changes in diaphragm function in high-altitude natives, such that highlanders in chronic hypoxia maintain similar diaphragm function to lowlanders in sea level conditions.

Cell responses evoked by tooth pulp stimulation above the marginal layer of the cat's trigeminal nucleus caudalis.

In cats anesthetized with urethane, all-or-nothing, synaptically evoked recordings were made from 80 separate units in the descending spinal tract of the trigeminal nerve above the left trigeminal nucleus caudalis, at depths not exceeding 50 micrometer from the surface of the medulla. The units were excited by the left upper (21), left lower (25), either (28), or only on simultaneous stimulation of both (six) canine tooth pulps. There was no somototopic distribution. The latency of responses ranged from 4 to 82 msec. For the group of 28 units excited by upper and lower tooth pulps, there was close matching of response latencies from the two teeth. An abrupt decrease in latency upon increasing stimulation strength ("jumping"), and a gradual increase in latency during repetitive stimulation at a frequency between 1 and 20 Hz ("drifting") was characteristic of most, but not all, responses. Units evoked by stimulation of the inferior dental or infraorbital nerves had similar characteristics. Stimulation of a tooth pulp at threshold for a particular unit was used to test the excitability of that unit after suprathreshold stimulation of the same or a different canine tooth pulp. Stimulation of the upper left canine tooth pulp was generally only facilitatory, while stimulation of the lower left canine tooth pulp was initially facilitatory and later inhibitory. Stimulation of the upper or lower right canine tooth pulps did not excite but could inhibit units excited by the left canine tooth pulps. There was a significant correlation between the frequency at which a unit would follow repetitive stimulation and the duration of the inhibition generated by the first of a pair of stimuli. Long inhibition was associated with poor frequency following.

Brain stem projections of the glossopharyngeal nerve and its carotid sinus branch in the rat.

Transganglionic transport of horseradish peroxidase or lectin-conjugated horseradish peroxidase from an application site in the cervical trunk of the glossopharyngeal (IXth cranial) nerve of the rat produced extraperikaryal reaction product characteristic of axon terminal processes in three regions of the brain stem: (1) the nucleus of the tractus solitarius, from approximately 2.5 mm rostral to the obex to approximately 3 mm caudal to the obex; (2) the spinal trigeminal nucleus at the level of obex; (3) the cuneate fasciculus, approximately 3 mm caudal to the obex. In contrast, labelling of the carotid sinus nerve, a branch of the glossopharyngeal nerve which conveys chemoreceptor and baroreceptor afferent fibers from the carotid bifurcation, revealed a restricted central projection to within 1 mm of the obex and corresponding to the intermediate region of the glossopharyngeal nerve projection to the nucleus of the tractus solitarius. Two distinct aggregations of label were observed: (1) rostral to the obex, within the lateral and dorsomedial subnuclei of the nucleus of the tractus solitarius; (2) caudal to the obex, within the commissural and ventrolateral subnuclei of the nucleus of the tractus solitarius. Between these two sites the density of labelling was reduced. Retrogradely labelled neurons were demonstrated in the inferior salivatory nucleus and in the nucleus ambiguus after application of lectin-conjugated horseradish peroxidase to the glossopharyngeal nerve. Of the labelled neurons in the nucleus ambiguus (approximately 100), 25% contributed fibers to the carotid sinus nerve. The concentration of extraperikaryal reaction product located rostral to the obex after labelling of the carotid sinus nerve closely matches descriptions of the region of afferent terminations from carotid and aortic baroreceptors in the cat. The concentration of label caudal to the obex may therefore correspond to the region of afferent terminations from carotid chemoreceptors. This study may therefore provide some basis for a separation of the central synapses of primary afferent fibers from the carotid baroreceptors and chemoreceptors in the rat. The labelled neurons of the nucleus ambiguus provide the anatomical substrate for centrifugal control of carotid chemoreceptor activity.

Inhibitory controls on thermal neurones in the spinal trigeminal nucleus of cats and rats.

Although electrical stimulation of supraspinal structures and local large fibres is known to inhibit the responses of nociceptive neurones, comparable studies on thermoreceptive cells have not been made. We have studied the effects of nucleus raphe magnus (NRM) and segmental stimulation on cold and warm responsive neurones in trigeminal nucleus caudalis of both the rat and cat. All 48 neurones (46 cold and 2 warm) tested in the cat and 24 cold neurones in the rat were unaffected by the NRM at a variety of stimulation parameters. However, segmental stimulation inhibited 4/20 neurones in the cat and 11/26 cells in the rat. The results show the selectivity of the inhibition following NRM stimulation.

Pre-spinal convergence between thoracic and visceral nerves of the rat.

Dichotomizing sensory axons have been demonstrated in a number of species and are of significance in understanding the possible mechanisms underlying referred pain. The present study reviews work employing fluorescent dyes as tracers to demonstrate afferent dichotomization in the peripheral nervous system. Dichotomization between the intercostal and splanchnic nerves of the rat was demonstrated by means of intraneural transport of Diamidino yellow or Fast blue. Frequency of pre-spinal somato-visceral convergence averaged 2% (range 0.1-21%). Average frequency of convergence was 8.3% (range 2-23.1%) between internal and external intercostal nerves. Control experiments in which axoplasmic transport was inhibited by vinblastine ruled out the possibility of errors from non-axoplasmic transport of the markers. Thoraco-visceral pre-spinal convergence occurs in the rat and is variable in extent.

Need satisfaction in terminal care settings.

Research comparing hospice and conventional programs of care for the terminally ill has identified few measurable differences in the care provided to patients and their families. Nonetheless, hospice recipients frequently express a higher level of satisfaction with their program of care. This study compared the ability of hospice and conventional care settings to meet the basic emotional needs of families during a member's dying and death from cancer. In addition, the relationship of basic needs satisfaction, perceptions about the nurse, and overall satisfaction with the program of care were explored. One hundred bereaved familial care givers completed a mail questionnaire concerning their perceptions of care at the site of a family member's death. The sites were (1) the home, with care provided by a Medicare certified, community-based hospice program: (2) a hospital affiliated with a Medicare certified, community-based hospice program; (3) a hospital with its own hospice program; and (4) a conventional (non-hospice) hospital. Analyses of quantitative data supported two hypotheses about significant differences between hospice and conventional care. The conventional care group demonstrated the lowest levels of basic needs satisfaction, satisfaction with the psycho-social support of the nurse, and overall program satisfaction. As predicted, overall satisfaction with care was consistent across hospice groups. However, home hospice care provided the highest quality of basic needs satisfaction and the highest level of satisfaction with the nurse. Significant Pearson correlations supported the hypothesis that overall satisfaction is negatively related to unmet basic needs (r = -0.69) and positively related to the psycho-social support received from nurses (r = 0.73).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of therapeutic muscle stretch on neural processing.

Therapeutic muscle stretch is a commonly used procedure despite little evidence in support of efficacy or information about the mechanisms underlying the various methods. The purpose of this work was to compare the sequential application of static and ballistic muscle stretch with static muscle stretch alone, using the electrically elicited Hoffmann reflex (H-reflex) as a measure of excitability of homonymous motoneurons. The foot was passively dorsiflexed and either maintained in this position or rapidly and repeatedly dorsiflexed at a velocity of 1.0 radian/sec. Hoffmann reflexes were taken using established criteria under control conditions and during stretch conditions. An analysis of variance indicated a significant difference (p < 0.05) between condition means, with H-reflex amplitude reducing to 60 and 15% of the control value during static and ballistic stretch, respectively. Since reductions in alpha-motoneuron pool excitability correlate with increased flexibility, ballistic stretch applied following static stretch appears more effective than static stretch alone.

Thermoregulation during mild exercise.

A comparison was made of the thermoregulatory effects of wearing black or white clothing during exercise under radiant heating. For subjects in black clothing the skin temperature was higher than with white but the rectal temperature and heart rate were lower.

Use of sublingual glyceryl trinitrate as a supplement to volatile inhalational anaesthesia in a case of uterine inversion.

We present a case of uterine inversion in which glyceryl trinitrate was used via the sublingual route, as opposed to the intravenous route, in association with volatile inhalational anaesthesia in order to achieve relaxation of the uterus. A transient, but significant, hypotensive response occurred, which was easily corrected with a colloid infusion and vasopressors. Sublingual glyceryl trinitrate is easily administered, has a fast onset of action and may have a role in situations where rapid relaxation of the uterus is required.

Sacroiliac joint manipulation decreases the H-reflex.

Joint manipulation is widely utilized clinically to decrease pain and increase the range of motion of joints displaying limited mobility. Evidence of efficacy is based on subjective reports of symptom improvement as well as on the results of clinical trials. Experiments were designed to determine whether or not sacroiliac joint manipulation affects the amplitude of the Hoffman (H) reflex. Surface EMG recordings of the reflex response to electrical stimulation of the tibial nerve in the popliteal fossa were made from the soleus muscle. The averaged amplitudes of H-reflexes were compared on both legs before and after either sacroiliac joint manipulation or a sham procedure. H-reflex amplitude was significantly decreased (12.9%) in the ipsilateral leg (p < 0.001) following a sacroiliac joint manipulation while there was no significant alteration following the sham intervention. There was no significant alteration in reflex excitability in the contralateral leg to the sacroiliac joint manipulation. To further investigate the mechanism of these reflex alterations, the local anaesthetic cream EMLA (Astra Pharmaceuticals) was applied to the skin overlying the sacroiliac joint and the experiments were repeated on a different group of subjects. This was intended to determine if excitation of cutaneous afferents was responsible for the reflex excitability changes. There was still a significant decrease in reflex excitability (10.6%) following sacroiliac joint manipulation (p < 0.001). These findings indicate that joint manipulation exerts physiological effects on the central nervous system, probably at the segmental level. The fact that the changes persisted in the presence of cutaneous anaesthesia suggests that the reflex changes are likely to be mediated by joint and/or muscle afferents.

Effects of environmental temperature on the development of a noradrenergic thermoregulatory mechanism in the rat.

Rats reared at 30 degrees C do not exhibit the same thermoregulatory competence during cold exposure as do rats reared at 20 degrees C. They are even more clearly distinguished by the absence of an hypothermic response to intrahypothalamic noradrenaline (IH-NA). In one series of experiments, different groups of rats all received 120 days 30 degrees C-exposure and 20 days 20 degrees C-exposure. The 20 degrees C-exposure occurred at different ages in different treatment groups. At 140 days of age, bilateral IH-NA injections (each 10 micrograms/1 microliter CSF) were administered in conscious rats and the body temperature response observed. An hypothermic response to IH-NA was observed in groups whose exposure to 20 degrees C terminated between 20 and 80 days of age. In a second series of experiments, duration of rearing at 20 degrees C varied but always started at 40 days of age. Responses to IH-NA in 140-day-old adults indicated that the exposure required to induce 50% of the hypothermic response of control (20 degrees C-reared) rats was approximately 17 days. These data suggest that there is an hypothalamic noradrenergic mechanism implicated in the control of body temperature whose development is affected by environmental temperature in a duration-dependent manner. The period during which this effect may be exerted extends into adulthood.

Static and dynamic response characteristics, receptive fields, and interaction with noxious input of midline medullary thermoresponsive neurons in the rat.

Thermal clamping of deep-body temperature and 16 fields covering the total truncal skin surface enabled characterization of thermal transmission neurons distributed in a midline medullary location. The total data set comprised 136 neurons from 54 female rats. Relative abundance of neuronal types was 27 to 34 to 75 for cold-responsive, warm-responsive, and thermally unresponsive neurons. Response maxima of thermoresponsive neurons to static thermal stimulation of the total truncal surface were 55 +/- 4 ips (mean +/- SE) at 5 degrees C for cold-responsive neurons and 6.0 +/- 1.6 ips at 35 degrees C for warm-responsive neurons. Dynamic thermal stimulation of the total truncal surface at rates up to +/- 1.6 degrees C/s failed to reveal a clear dynamic thermosensitivity in either cold- or warm-responsive neuronal pools. Instead, the data suggest a preferential passing of the static response relative to the dynamic response. Cutaneous thermal receptive fields were diffuse, occupying most of the truncal surface. Subparts of these fields drove thermoresponsive neurons to variable extents, suggesting convergence from unequally represented multiple cutaneous sources. Noxious stimulation at widely distributed body sites consistently augmented activity in cold-responsive neurons. A thermoregulatory rather than somatesthetic role is proposed for the midline medullary neurons studied here.

The dynamic properties of trigeminal thermoreceptors following heat-rearing in rats.

Dynamic properties of thermoresponsive units at the caudal trigeminal nucleus are not modified by heat-rearing. The modification of the thermoregulatory system by heat-rearing is unlikely to be a consequence of altered thermoreceptive function at this level. Rats were reared at ambient temperatures of 30 degrees C (heat-reared) and 20 degrees C (controls). Extracellular recordings of thermoresponsive units at the caudal trigeminal nucleus were made while the facial receptive fields of these thermoresponsive units were stimulated with 6 different rates of temperature change (+0.5, +0.1, +0.02, -0.02, -0.1 and -0.5 degrees C/sec). All thermoresponsive units encountered were cold-sensitive. The static maxima were clustered around 13.5 degrees C and did not differ between treatment groups. Dynamic maxima occurred at temperatures around 29-30 degrees C and were not different in thermoresponsive neurones from the two treatment groups. There was no difference between the two treatment groups in the dynamic activity of trigeminal cold-responsive neurones at any of the 42 combinations of temperature and rate of temperature change examined.

Initiation and inhibition of shivering in the rat: interaction between peripheral and central factors.

1. Unanaesthetized, female white laboratory rats were subjected to almost square-wave changes in ambient temperature, from 20 degrees C to 35 degrees C, in a small climatic chamber. 2. Intracerebroventricular injections of serotonin and methysergide were made in shivering, unanaesthetized rats. 3. The integrated electromyogram of m. suprascapularis was recorded as a quantitative measure of shivering activity to monitor the effects of the above procedures. 4. Both warm transients and serotonin inhibited shivering, but methysergide blocked only the effect of serotonin.

Evidence for on-off control of heat dissipation from the tail of the rat.

Anterior hypothalamic temperature, tail vasoactivity, and tail heat loss were observed in unanaesthetised rats resting at an ambient temperature that was varied between 25 and 35 degrees C between experiments, but was held constant within an experiment. Vasodilation and vasoconstriction at the tail were qualitatively detectable by the appearance and disappearance of temperature differences between the tail surface overlying the ventral arterial supply, and the lateral venous drainage. Vasodilation detected this way was an abrupt singular event (being either on or off), and preceded subsequent exponential changes in tail surface temperature and heat loss. Within the ambient temperature range of 29--33 degrees C, the following sequence occurred in a 20-min cycle, despite the noncycling constant environmental and metabolic heat loads: tail vasodilation - 0.2 to 0.4 degrees C fall in hypothalamic temperature - tail vasoconstriction - 0.2 to 0.4 degrees C rise in hypothalamic temperature. This behaviour, consistent with the limit-cyclic behaviour of some nonlinear controllers, as well as the abrupt two-state nature of vasoactivity at the rat tail, provides evidence that the mechanism can be described by an on-off control model. In addition, angiography suggests that vasoconstriction rather than countercurrent heat exchange provides the major barrier to core to tail heat flow during the "off" phase.

The assessment of intramuscular discrimination using signal detection theory: its potential contribution to chiropractic.

INTRODUCTION: Most studies on sensory changes after manual therapies have focused on pain sensitivity. This ignores the wider range of sensory alternations that may be important in assessing patient functioning and neglects the issue of bias, which is inherent in most methods of pain assessment employing threshold methodology. Signal detection theory (SDT) addresses the issue of bias and provides a measurement of intramuscular discrimination--the ability to discriminate between two stimuli--which can be assessed over the full range of sensation. This paper will discuss the strengths and limitations of SDT and report on the effects of trigger point therapy and manipulation on intramuscular discrimination to illustrate the potential contribution of this methodology to chiropractic. METHODS: Intramuscular needle electrodes were used to provide a pair of electrical stimuli to the forearm extensor muscles. Subjects were asked to assess the differences between stimuli before and after treatment. The treatments consisted of manual trigger point therapy applied to the forearm extensors, cervical spine manipulation and a control treatment. RESULTS: After the trigger point therapy, there was a significant improvement in the ability of the subjects to discriminate between intramuscular signals to treated muscle. Some individual subjects showed alterations in ability to discriminate after cervical spine manipulation but the effect was not significant in the group as a whole. CONCLUSIONS: The methodology of signal detection theory provides a promising, bias-free method of assessing changes in intramuscular sensation after various treatments. In these experiments, trigger point therapy was found to enhance intramuscular discrimination, suggesting that a peripheral reflex may be involved.