云南北部金沙江流域小兽体表恙螨种类及空间分布格局研究

[目的]了解云南北部金沙江流域恙螨的种类组成、优势种及其种群空间分布格局等。[方法]选择云南北部金沙江流域的巧家、绥江两县的农舍、农田、灌木丛和森林4种生态环境诱捕小兽,选择小兽耳窝和臀部位作为恙螨固定采集部位,用镊子取耳窝和臀部的全部恙螨,70%乙醇固定,Hoyer液封片后于显微镜下鉴定种类。用扩散系数、丛生指数、Cassie指数及聚块指数等指标评价种群空间分布格局。[结果]共捕获小兽302只,经分类鉴定地隶属7目13属16种。共采集恙螨4550只,经分类鉴定隶属3亚种12属63种。大多数小兽体表恙螨种类较丰富,最高的达42种。优势种为攸氏无前恙螨、微板无前恙螨、小板纤恙螨、中华纤恙螨和乡野纤恙螨等,它们占恙螨总数的75.68%。所有优势种在其对应主要宿主体表的4个种群空间分布格局参数都大于相应的界限值0或1,均为聚集型分布。[结论]云南北部金沙江流域恙螨数量丰富,种类复杂。恙螨在小兽体表呈群居寄生。     

Airflow synchronous with oscillatory acceleration reflects involuntary respiratory muscle activity

To explore mechanisms causing involuntary airflow synchronous with oscillatory axial whole body acceleration (oscillatory axial acceleration, OAA) such as that during locomotion, we monitored airflow, acceleration, and electromyograms (EMGs) of the rib cage and abdominal muscles in standing subjects undergoing OAA at 3, 6, and 9 Hz at accelerations of 0.1-0.95 g. Subjects relaxed or performed static respiratory maneuvers at constant lung volume with glottis open. Oscillatory airflows (0.01-3.01 s(-1)) synchronous with OAA were not consistent with expectations for a passive respiratory system, and were larger during active respiratory efforts than during relaxation. Peak inspiratory airflow usually preceded peak upward acceleration by 90-180 degrees. In 80% of runs with respiratory muscles voluntarily activated or relaxed, EMGs showed activity synchronous with OAA. Changes in periodic muscle activity coincided with changes in oscillatory airflow. We conclude that periodic muscle activity, probably a reflex response to body wall deformation during OAA, strongly influences the involuntary airflow synchronous with OAA.     

Effects of gadolinium chloride on slowly adapting and rapidly adapting receptors of the rabbit lung

Effects of gadolinium chloride, an inhibitor of stretch-activated channels, on the responses of slowly adapting receptors (SARs) and rapidly adapting receptors (RARs) to hyperinflation were investigated. The increase in activity of RARs resulting from sustained elevations of left atrial pressure (LAP) was also assessed with gadolinium chloride application. Action potentials (AP) of SARs and RARs during hyperinflation were recorded from the vagus nerve of anesthetized New Zealand White rabbits before and after application of gadolinium chloride (20mM) directly on the receptor area of the nerve endings. There was a significant reduction of activity in SARs (n = 9) and RARs (n = 7) after application of gadolinium chloride. Activity of RARs (n = 6) increased when the LAP was elevated by 5 and 10 mmHg. This effect was abolished after gadolinium chloride was applied to receptor endings and the activity was restored when gadolinium chloride was removed. This suggests that stretch-activated channels play a role in SARs and RARs activity.     

Hypoxic response in newborn rat is attenuated by neurokinin-1 receptor blockade

Substance P (SP) is considered to be involved in the regulation of respiration, in particular when respiratory demands are increased, such as during hypoxic stress. In the present study we have investigated the effects of intracerebroventricular pre-treatment with the selective NK-1 receptor antagonist RP67580 on the respiratory response to hypoxia in 5-day-old rat pups. Basal respiration was not altered by RP67580. When subjected to hypoxia (10% O(2)), rat pups pre-treated with RP67580 were unable to sustain the increased respiratory frequency at 10 min. In situ hybridisation demonstrated increased expression of c-fos mRNA in several brainstem areas following hypoxia. This activation was blocked by the antagonist in the retrotrapezoid nucleus and the rostral ventrolateral medulla, areas known to be involved in the hypoxic ventilatory response. This study corroborates a role of endogenously released SP, mediated via NK-1 receptors, in the sustained response to hypoxia in 5-day-old rat pups and suggests that neurons in the rostral ventrolateral medulla are important in this function. It also represents a further example that neuropeptides are released under stressful conditions.     

Hypometabolism in reptiles: behavioural and physiological mechanisms that reduce aerobic demands

During exposure to hypoxia all vertebrates utilize a suite of cardiovascular and ventilatory responses that, in combination, strive to maintain adequate delivery of oxygen to the metabolizing tissues. In addition to maintaining oxygen delivery through cardio-respiratory responses, oxygen demands in the tissues can also be reduced. Reptiles use this alternative strategy during periods of moderate to severe hypoxia by behavioural reductions in preferred body temperature and by active down-regulation of aerobic metabolism. Below we review these two different strategies and discuss their possible mechanisms and physiological significance.     

Lung-deflating ability of rib cage and abdominal muscles in rabbits

Anesthetized, apneic, mechanically ventilated rabbits were placed into a tilting plethysmograph that a rubber diaphragm, tightly fitting the animal's body just below the xiphoid process, separated into a rib cage and abdominal chamber. Expired volumes (DeltaV) and abdominal pressure changes (DeltaPab) were assessed in supine and upright posture during maximal rib cage (RCC) and/or abdominal compression (ABC) by pressurizing either or both chambers, and during maximal stimulations of abdominal muscles (ABS). With RCC, DeltaV supine and upright amounted to 16+/-4.9 (mean+/-S.D.) and 20.9+/-7% of the vital capacity in supine posture (VCs) and to 75.8+/-14.5 and 44.8+/-13.9% of the expiratory reserve volume (ERV) in corresponding posture, DeltaPab being negligible. With ABC, DeltaV was 13.7+/-2 and 38.9+/-7.3% VCs and 68.4+/-14.8 and 84.4+/-10.5% ERV, respectively. Both DeltaV and DeltaPab were similar with ABC and ABS, independent of posture. If this applies also to RCC and expiratory rib cage muscle contraction, maximal expiratory effects of the latter (a) are larger in upright than supine posture; (b) contribute to ERV more in supine than upright posture; and (c) are similar to those caused by ABS in supine, but substantially smaller in upright posture.     

Validity of the allometric cascade model at submaximal and maximal metabolic rates in exercising men

The dependence of metabolic rate (MR) on body mass (M) is described by the general allometric equation MR=aM(b), where, a is a proportionality coefficient and b is the mass exponent. Darveau et al. [Nature 417 (2002), 166] proposed a novel 'multiple-causes' allometric cascade model as a unifying principle of the scaling of MR, at rest and during maximal exercise. We tested the validity of body mass exponents predicted from the model for submaximal and maximal aerobic exercise conditions in 1629 men. MRs were estimated from whole-body oxygen consumption during an incremental treadmill test to voluntary exhaustion. For both submaximal (b=0.83) and maximal (b=0.94) exercise requiring average oxygen consumption rates of around 5-11 times resting values, respectively, the obtained mass exponents were remarkably consistent with predicted values. Moreover, for maximal MR the global mass exponent was significantly greater than for submaximal aerobic metabolism, congruent with the allometric cascade model.     

Arterial hypoxemia in exercising thoroughbreds is not affected by pre-exercise nedocromil sodium inhalation

It has been reported that pulmonary injury (i.e. capillary stress failure) evoked histamine release from airway inflammatory/mast cells contributes to exercise-induced arterial hypoxemia (EIAH) and that pre-exercise inhalation of nedocromil sodium mitigated EIAH in human subjects 'Med. Sci. Sports Exercise 29, (1997) 10-16'. Because exercise-induced pulmonary hemorrhage due to capillary stress failure is routinely observed in racehorses, we examined whether nedocromil inhalation would similarly benefit EIAH and desaturation of hemoglobin in horses. Two sets of experiments, namely, placebo studies followed in 7 days by pre-exercise nedocromil sodium (30 puffs=60 mg) inhalation experiments were carried out on 7 healthy, sound, exercise-trained thoroughbred horses. In both treatments, arterial and mixed-venous blood-gas/pH measurements were made at rest pre- and post-placebo/drug inhalation, as well as during incremental exercise leading to galloping at 14 m/sec on a 3.5% uphill grade-a workload that elicited maximal heart rate and caused pulmonary hemorrhage in all horses in both treatments, thereby indicating capillary stress failure had occurred. In both treatments, significant (P<0.0001) EIAH of a similar magnitude had developed by 30 sec of maximal exertion, and further significant changes in arterial O(2) tension did not occur as exercise duration progressed to 120 sec. Thus, pre-exercise inhalation of nedocromil sodium was ineffective in modifying the development and/or severity of EIAH in the present study. These findings argue against the airway inflammatory mediator(s) release hypothesis for causing arterial hypoxemia in racehorses.     

Substance P inputs to laryngeal motoneurons in the rat

Substance P terminals have previously been demonstrated around retrogradely labelled posterior cricoarytenoid (PCA) motoneurons, but little is known regarding substance P inputs to other functionally identified laryngeal motoneurons. In the present study, we determined the number and distribution of close appositions between substance P immunoreactive boutons and three types of laryngeal motoneuron by using a combination of intracellular recording, dye-filling and immunocytochemistry in the rat. Cricothyroid (CT) motoneurons received 15+/-5 substance P appositions/neuron (mean+/-S.D., n = 6), PCA motoneurons received 13+/-5 (n = 6), and laryngeal constrictor (LCS) motoneurons received 11+/-4 (n = 5). In contrast to our previous finding of a preferential serotonin innervation of CT motoneurons, we found no significant difference between the substance P inputs to CT, PCA and LCS motoneurons. Our results indicate a modest role for substance P in control of laryngeal motoneuronal function.     

Respiratory muscle electromyogram and mouth pressure during isometric contraction

When extra-diaphragmatic muscles are activated progressively under approximately isometric conditions, we expect a corresponding increase in respiratory muscle output. Therefore, we examined relative recruitment shown as the latency to onset of EMG activity, and the relationship between mouth pressure and electromyogram activity of the neck accessory and transversus abdominis (TRANS) muscles during respiratory maneuvers against occlusion. Fine wire electrodes were inserted into the scalene (SCLN), sternocleidomastoid (STERNO), trapezius (TRAPZ) and TRANS in six awake, healthy subjects. Mouth pressure, raw and moving average EMG signals were recorded during gradual production of expiratory or inspiratory mouth pressure to maximum (MPmax) at FRC in the standing posture. Group mean linear regression lines of EMG activity versus mouth pressure were strongly significant for SCLN and TRANS, less for STERNO, and least for TRAPZ. The SCLN and STERNO showed EMG activities with low, and TRAPZ showed EMG activity only with high, mouth pressure. At 90% MPmax, TRAPZ was much less active compared with TRANS, SCLN, or STERNO. These results suggest that over a wide range of respiratory effort there is a significant difference in the relationship between mouth pressure and EMG activity in the accessory muscles, with differential recruitment of individual respiratory muscles.