Comparative study of the innervation patterns of the hyobranchial musculature in three iguanian lizards: Sceloporus undulatus, Pseudotrapelus sinaitus, and Chamaeleo jacksonii

The neuroanatomy and musculature of the hyobranchial system was studied in three species of iguanian lizards: Sceloporus undulatus, Pseudotrapelus sinaitus, and Chamaeleo jacksonii. The goal of this study was to describe and compare the innervation and arrangement of the hyobranchial musculature in the context of its function during tongue protrusion. A comparison of the hyobranchial innervation patterns revealed a relatively conserved innervation pattern in S. undulatus and P. sinaitus, and a modified version of this basic layout in C. jacksonii. All three species show anastomoses between sensory neurons of the trigeminal nerve and motor neurons of the hypoglossal nerve, suggesting that feedback may be important in coordinating tongue, jaw, and hyoid movements. The hyobranchial musculature of S. undulatus is very similar to that of P. sinaitus; however, there are minor differences, including the presence of an M. genioglossus internus (GGI) muscle in S. undulatus. Further differences are found mainly in functional aspects of the hyobranchial musculature, such as changes in the muscle lengths and the origins and insertions of the muscles. In C. jacksonii the hyobranchial system is comprised of largely the same components, but it has become highly modified compared to the other two species. Based on the innervation and morphological data gathered here, we propose a revision of the terminology for the hyobranchial musculature in iguanian lizards.     

Adaptive changes in the thermogenesis of rats by cold acclimation and deacclimation

Male Wistar rats, aged 6 weeks, were maintained at 25 degreesC for 9 to 11 weeks (W group), at 10 degreesC for 9 to 11 weeks (C group), and at 25 degreesC for 2 weeks after exposure to 10 degreesC for 9 weeks (D group). Thermogenesis at 10 degreesC was significantly greater than at 25 degreesC. Thermogenesis per body mass in the C group was greater than in the W and D groups. The RQ value at 10 degreesC was greater than at 25 degreesC in the W group, whereas the opposite was observed in the C and D groups. It is suggested that a large part of enhanced thermogenesis, caused by cold acclimation for 9 weeks, is lost because of a decreased secretion of calorigenic hormones, in spite of a slight decrease in BAT mass, during deacclimation for 2 weeks.     

Decay of heat acclimation during exercise in cold and exposure to cold environment

Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0°C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO_2max in the heat (Ta: 31.1°C, RH: 70%). Rectal temperature (T _re) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399–408, 1977). After HA (day 16) T _re and HR decreased significantly. During DA, EXG showed decay in T _re of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T _re and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T _re and 12% in HR, while EPG showed gains of 47% in T _re and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T _re after 4 days of DA.     

Alterations in neurofibrillar rings in the lizard brain during cold acclimation

Summary Neurofibrils were compared in warm (30 °C) acclimated (H) and cold (6 °C) acclimated (C) lizards (Sceloporus) by reduced silver staining. In H and C sections stained simultaneously by Bodian's protargol method, the neurofibrils: are generally equivalent along the lengths of dendrites and axons, are thicker and fewer in large multipolar neurones in C sections, and are many times more numerous as rings (boutons) in synaptic regions of the C sections. The morphology of the rings in C and H sections is similar, and no indication of abnormal rings or argyrophilic granules indicating degeneration is present. Comparison of rings per unit volume (10⁴m³) show characteristic ratios for each synaptic region varying from 35:12 (CH) in the large-celled layer of the hippocampus to 602 in the cerebellar molecular layer. Counts of over 60 rings in 10⁴m³ are routinely present in most major synaptic regions in C sections whereas the H sections do not show ring counts above 20/10⁴m³ in any region. It is concluded that the experimentally induced alterations in number of neurofibrillar rings represents a specific response of some neuronal elements to thermal stress.     

The oculomotor and trochlear nuclei in the one humped camel (Camelus dromedarius).

Literature on the organization of the oculomotor and trochlear nuclei of large animals is scanty. There were no reports on the organization of the oculomotor and trochlear nuclei of the camel, hence this study. Nine brains were used for the study. The brainstems were double-embedded in celloidin and paraffin and were cut serially at 24 microns and stained with toluidine blue. Light microscopic studies of the nuclei showed that the principal oculomotor nuclei were not subdivided and were composed of large multipolar nerve cell bodies that had a mean length of 30 +/- 5 microns. The nucleus was 2.4 mm long, 0.7 mm wide and 1.1 mm high. The Edinger-Westphal nucleus was small and was made up of elongated oval cell bodies that had a mean length of 33 +/- 5 microns and a mean diameter of 10 +/- 2 microns. The trochlear nucleus was located caudal to the oculomotor nucleus from which it was separated by a gap. The nerve cell bodies of the trochlear nuclei were similar to those of the oculomotor nuclei. The cell bodies had a mean length of 20 +/- 2.5 microns and a mean width of 18 +/- 3 microns. The caudal central nucleus was indistinct. It was concluded, that the oculomotor and trochlear nuclei of the camel are similar in their general organization to those of other animals but differences exist in the development and organization of the component parts.     

低氧习服过程中大鼠心脏的适应性改变

目的:观察在低氧习服过程中,大鼠心肌毛细血管密度、血流供应和心脏功能的变化规律。方法:大鼠在5000m模拟高原低氧5、15d和30d后,用碱性磷酸酶(ALP)组织化学方法显示心肌毛细血管并进行图象分析;用放射性微球法测定心肌血流量;用心导管技术测定左、右心室功能。结果:在低氧习服过程中,整个右室心肌血流量显著增加,功能显著增强。低氧15d后,右室心肌毛细血管密度虽无明显变化,但单位面积内毛细血管数与肌纤维数的比值(C/M)显著增高。低氧5d时左室心肌血流量虽显著增加,但左室功能明显降低;随着低氧时间的延长,左室心肌血流量和左室功能恢复正常。在低氧30d时,左室心肌毛细血管密度和C/M比值均显著增高。结论:大鼠在对低氧习服过程中,右室心肌血流量持续增加、心肌肥大并伴有毛细血管增生及功能增强;左室先有心肌血流量增多和心功能降低,后来心肌血流量恢复并出现毛细血管增生,同时左室功能恢复。     

Basic fibroblast growth factor (bFGF) contributes to the enlargement of brown adipose tissue during cold acclimation

The contribution of basic fibroblast growth factor to brown adipose tissue (BAT) enlargement during cold acclimation was investigated using rat brown adipocytes in primary culture. After cold exposure (at 5° C) for 28 days, the level of bFGF messenger ribonucleic acid (mRNA) in BAT of cold-acclimated rats was markedly increased with the increase in the BAT weight. In addition, the blood plasma from cold-acclimated rats considerably enhanced the expression of basic fibroblast growth factor mRNA in rat brown adipocytes. Likewise, the blood plasma from cold-acclimated rats significantly stimulated the growth of rat brown adipocyte precursor cells compared with that from warm-acclimated rats, whereas there was no difference of effect between the two blood plasmas on the growth of bovine capillary endothelial cells. Basic fibroblast growth factor, but not platelet-derived growth factor stimulated the growth of brown adipocyte precursor cells. The conditioned medium from brown adipocyte primary culture markedly stimulated the growth of bovine capillary endothelial cells and the effect was inhibited considerably by antibasic fibroblast growth factor antibody. These results suggest that some factors concerned with the growth of brown adipocyte precursor cells are present in the blood plasma from cold-acclimated rats, and that basic fibroblast growth factor produced by brown adipocytes may significantly contribute to BAT enlargement by autocrine mechanisms during cold exposure.     

Effects of cold acclimation on cold-induced changes in lipid metabolism of rat brown adipose tissue.

Effects of acute cold exposure (0 degree C, 12 h) on lipid metabolism of the interscapular brown adipose tissue (BAT) were studied in warm controls (25 degrees C) (WC) and cold-acclimated rats (5 degrees C, 4 weeks) (CA). 1) We confirmed that cold acclimation brought about decreased BAT triglyceride (TG) level and increased BAT phospholipid (PL) level. The indexes of unsaturation, such as unsaturation index and polyunsaturated fatty acids/saturated fatty acids ratio, of bulky fatty acids (FA) (palmitic, stearic, oleic, and linoleic acids) decreased in TG, while those increased in PL. Rare FA (eicosadienoic acid, homo-gamma-linoleinic acid, lignoceric acid) level, which were about five times higher in PL than TG in WC, decreased in both TG and PL in CA. 2) Effect of acute cold exposure in WC: The level as well as the amount of TG in BAT was greatly reduced and the indexes of unsaturation in TG-FA increased. The most part of reduced TG (85%) was explained by the bulky FA. Rare FA explained only 1.1% of reduced TG. PL level in BAT did not change, but its amount decreased. The indexes of unsaturation increased in PL-FA. 3) Effect of acute cold exposure in CA: CA was placed in warm temperature of 25 degrees C before cold exposure. In contrast with the cold-reduced TG in WC, either the level or the total amount of TG in BAT did not change, but the indexes of unsaturation in TG-FA decreased. The level as well as the total amount of PL in BAT increased. The arachidonic index and arachidonate in PL-FA decreased, but the indexes of unsaturation did not change. These results indicate as a whole that acute cold exposure as well as cold acclimation influences BAT lipid metabolism in FA compositions as well as amount of TG and PL, suggesting that such changes are related to thermogenic activity of this tissue.     

Process- and controller-adaptations determine the physiological effects of cold acclimation

Experimental results on physiological effects of cold adaptation seem confusing and apparently incompatible with one another. This paper will explain that a substantial part of such a variety of results may be deduced from a common functional concept. A core/shell treatment ("model") of the thermoregulatory system is used with mean body temperature as the controlled variable. Adaptation, as a higher control level, is introduced into the system. Due to persistent stressors, either the (heat transfer) process or the controller properties (parameters) are adjusted (or both). It is convenient to call the one "process adaptation" and the other "controller adaptation". The most commonly demonstrated effect of autonomic cold acclimation is a change in the controller threshold. The analysis shows that this necessarily means a lowering of body temperature because of a lowered metabolic rate. This explains experimental results on both Europeans in the climatic chamber and Australian Aborigines in a natural environment. Exclusive autonomic process adaptation occurs in the form of a better insulation. The analysis explains why the post-adaptive steady-state can only be achieved, if the controller system reduces metabolism and why in spite of this the new state is inevitably characterized by a rise in body temperature. If both process and controller adaptations are simultaneously present, there may be not any change of body temperature at all, e.g., as demonstrated in animal experiments. Whether this kind of adaptation delivers a decrease, an increase or no change of mean body temperature, depends on the proportion of process and controller adaptation.     

Morphologic changes in erythrocytes during exposure of the body to cold

Study of morphology of erythrocytes in residents of the Extreme North of the USSR and in experimental rats after prolonged effect of low temperatures established that the red blood system undergoes considerable rearrangement with the appearance of more marked polymorphism of erythrocytes. Adaptation reactions of the organism are accompanied by juvenation and increased destruction of erythrocytes simultaneously.     

Enhanced formation of cyclic AMP after cold acclimation in the rat

Plasma cAMP response to glucagon was enhanced after cold acclimation. Cold-acclimated rats also showed an enhanced production of hepatic cAMP in response to glucagon. In both brown and white fat tissues, cAMP contents increased after cold acclimation. Enhancement of cAMP formation in the liver and fat tissues may partly contribute to an enhanced nonshivering thermogenesis during cold acclimation.     

Ipsilateral and contralateral projections to the trochlear nucleus arise from different subdivisions in the vestibular nuclei

Vestibular neurons that project to the trochlear nucleus were studied following unilateral injections of horseradish peroxidase. After 48 h, the animals were perfused, transverse sections were cut, and reacted with diaminobenzidine. After injections centered on the trochlear nucleus, one-third of the labeled neurons were located in the ipsilateral superior (S) vestibular nucleus and almost half were in the contralateral medial (M) vestibular nucleus. Labeled fibers were restricted to the medial longitudinal fasciculus ipsilateral to the injection. This study supports hypotheses, based on physiological data of two vertical vestibulo-ocular pathways; one originating in the ipsilateral S that may be inhibitory and the second originating predominantly from the contralateral M that may be excitatory.     

大鼠伏膈核生后发育期形态学的变化

目的：探讨大鼠伏膈核的发育变化的形态学规律。方法：选取出生后一个月内不同时期的大鼠，常规切片染色后应用计算机辅助图像分析系统分别测量不同组别大鼠伏膈核细胞的密度及直径。结果：细胞直径随年龄呈增长趋势，至PD30已基本接近成年水平。细胞密度在PD0-PD15呈下降趋势，之后基本不再变化。结论：表明出生后一段时间内伏膈核细胞在形态上仍要经过一个不断成熟和完善的过程。     

Functions of the nucleus of the optic tract (NOT).

We studied the role of the nucleus of the optic tract (NOT) in adapting the gain of the angular vestibulo-ocular reflex (aVOR) in rhesus and cynomolgus monkeys using lesions and temporary inactivation with muscimol. The aVOR gain was adaptively reduced by forced sinusoidal rotation (0.25 Hz, 60 degrees/s) in a self-stationary visual surround, i.e., a visual surround that moved with the subject, or by wearing x0.5 reducing lenses during natural head movements. The aVOR gains dropped by 20-30% after 2 h and by about 30% after 4 h. Muscimol injections caused a loss of adaptation of contraversive-eye velocities induced by the aVOR, and their gains promptly returned to or above preadapted levels. The gains of the adapted ipsiversive and vertical eye velocities produced by the aVOR were unaffected by muscimol injections. Lesions of NOT significantly reduced or abolished the animals' ability to adapt the gain of contraversive aVOR-induced eye velocities, and the monkeys were unable to suppress these contraversive-eye velocities in a self-stationary surround. The lesions did not affect ipsiversive aVOR-induced eye velocities, and the animals were still able to suppress them. Lesions of NOT also affected the unadapted or "default" aVOR gains. After unilateral NOT lesions, gains of ipsiversive aVOR-induced eye velocity were reduced, while gains of contraversive aVOR-induced eye velocity were either unaffected or slightly increased. Consistent with this, muscimol injections into the NOT of unadapted monkeys slightly reduced the gains of ipsiversive and increased the gains of contraversive-eye velocities by about 8-10%. We conclude that each NOT processes ipsiversive retinal-slip information about visual surround movement relative to the head induced by the aVOR. In the presence of visual surround movement, the retinal-slip signal is suppressed, leading to adaptive changes in the gain of aVOR-induced contraversive horizontal eye velocities. NOT also has a role in controlling and maintaining the current state of the aVOR gains. Thus, it plays a unique role in producing and supporting adaptation of the gain of the horizontal aVOR that is likely to be important for stabilizing gaze during head movement. Pathways through the inferior olive are presumably important for this adaptation.     

Functions of the nucleus of the optic tract (NOT).

Ocular pursuit in monkeys, elicited by sinusoidal and triangular (constant velocity) stimuli, was studied before and after lesions of the nucleus of the optic tract (NOT). Before NOT lesions, pursuit gains (eye velocity/target velocity) were close to unity for sinusoidal and constant-velocity stimuli at frequencies up to 1 Hz. In this range, retinal slip was less than 2 degrees. Electrode tracks made to identify the location of NOT caused deficits in ipsilateral pursuit, which later recovered. Small electrolytic lesions of NOT reduced ipsilateral pursuit gains to below 0.5 in all tested conditions. Pursuit was better, however, when the eyes moved from the contralateral side toward the center (centripetal pursuit) than from the center ipsilaterally (centrifugal pursuit), although the eyes remained in close proximity to the target with saccadic tracking. Effects of lesions on ipsilateral pursuit were not permanent, and pursuit gains had generally recovered to 60-80% of baseline after about 2 weeks. One animal had bilateral NOT lesions and lost pursuit for 4 days. Thereafter, it had a centrifugal pursuit deficit that lasted for more than 2 months. Vertical pursuit and visually guided saccades were not affected by the bilateral NOT lesions in this animal. We also compared effects of these and similar NOT lesions on optokinetic nystagmus (OKN) and optokinetic after-nystagmus (OKAN). Correlation of functional deficits with NOT lesions from this and previous studies showed that rostral lesions of NOT in and around the pretectal olivary nucleus, which interrupted cortical input through the brachium of the superior colliculus (BSC), affected both smooth pursuit and OKN. In two animals in which it was tested, NOT lesions that caused a deficit in pursuit also decreased the rapid and slow components of OKN slow-phase velocity and affected OKAN. It was previously shown that slightly more caudal NOT lesions were more effective in altering gain adaptation of the angular vestibulo-ocular reflex (aVOR). The present findings suggest that cortical pathways through rostral NOT play an important role in maintenance of ipsilateral ocular pursuit. Since lesions that affected ocular pursuit had similar effects on ipsilateral OKN, processing for these two functions is probably closely linked in NOT, as it is elsewhere.