Hyperoxia increases paradoxical sleep rhythm in the pontine cat

Pontine cat is an ectothermic preparation, whose central temperature can artificially be lowered from 36 degrees C to 26 degrees C; this gradual hypothermia is accompanied by a dramatic increase in paradoxical sleep (PS). Two main hypotheses might explain this result: executive systems of PS might be switched on gradually by cold-sensitive thermodetectors, whereas inhibitory monoaminergic mechanisms appear to be warm-sensitive. On the other hand, energy saving mechanisms peculiar to hypothermia might promote PS appearance. Indeed, in normal animals, PS is selectively suppressed both by hyperthermia and hypoxia. The inhibitory effect of hypoxia might explain why hypothermia, which protects the brain against hypoxic alterations, might facilitate PS. If this last hypothesis is correct, the putative increase in cerebral oxygen supply might increase PS. For this reason, we submitted eight pontine carotid-deafferented cats, kept at the same central temperature (34 +/- 0.5 degrees C: temperature clamp) to periodic hyperoxia (PaO2 = 58 +/- 7 kPa) or room air (PaO2 = 17 +/- 2 kPa) alternatively during 4- or 12-h periods. Hyperoxia induced an 85% increase in PS, mainly due to an increase in PS rhythm (PS cycle duration was 65 +/- 4 min in normoxia and 45 +/- 4 min in hyperoxia, p<0.0001). In five animals, after hyperoxia, PS cycle returned gradually back to control values in 4 to 12 h. These findings show that PS is exquisitely sensitive to conditions that impair oxidative metabolism. The role of cholinergic executive PS systems as putative metabolic-sensitive neurons remains to be established.     

Analysis of the properties and functions of metal components

The properties of a metal component are analyzed and classified. It is established that the structure of the properties of some object may be described in terms of the determination of functions at different levels. The properties of metal components are analyzed and, on that basis, the concept of a function is defined. The concept of a component’s useful phase is introduced on the basis of the functional principle of property analysis. A design definition of the quality of metal products is proposed: the quality is the degree of fulfillment of three functions—transportation, installation, and operation. The methods of quality analysis based on investigation of the functions of the product over the duration of its useful phase also constitute the essence of functional–goal analysis. On the basis of this approach, the algorithm for quantitative quality assessment is improved. In the proposed approach, the stages of the life cycle are specified; the functions are arranged in a multilevel structure; and a single material body is regarded as a system of properties that will be differently expressed, depending on the purpose for which it is employed. Accordingly, functional–target analysis may be regarded as a new approach to studying the structure of the functions and properties of a metal component.     

富氧顶吹炼铅生产实践中喷枪损耗的原因分析及对策

主要阐述了富氧顶吹炼铅过程影响喷枪损耗的主要因素,进一步深入分析与总结了这些主要因素对喷枪损耗的影响情况,并在生产实践中采取相应的技术控制及改进措施,有效降低了喷枪的损耗,保证喷枪使用寿命达到了预期的要求,为富氧顶吹炼铅炉的正常运行奠定良好的条件。     

Role of melatonin in mediating seasonal energetic and immunologic adaptations

Winter is energetically demanding and stressful; thermoregulatory demands increase when food availability usually decreases. Physiological and behavioral adaptations, including termination of breeding, have evolved among nontropical animals to cope with the energy shortages during winter. Presumably, selection for the mechanisms that permit physiological and behavioral anticipation of seasonal ambient changes have led to current seasonal breeding patterns for many populations. In addition to the well-studied seasonal cycles of mating and birth, there are also significant seasonal cycles of illness and death among field populations of mammals and birds. Energetically challenging winter conditions can directly induce death via hypothermia, starvation, or shock; surviving these demanding conditions likely puts individuals under great physiological stress. The stress of coping with energetically demanding conditions may increase adrenocortical steroid levels that could indirectly cause illness and death by compromising immune function. Individuals would enjoy a survival advantage if seasonally recurring stressors could be anticipated and countered by bolstering immune function. The primary environmental cue that permits physiological anticipation of season is daily photoperiod, a cue that is mediated by melatonin. However, other environmental factors may interact with photoperiod to affect immune function and disease processes. Immune function is compromised during the winter in field studies of birds and mammals. However, laboratory studies of seasonal changes in mammalian immunity consistently report that immune function is enhanced in short day lengths. To resolve this apparent discrepancy, we hypothesize that winter stressors present in field studies counteract short-day enhancement of immune function. Prolonged melatonin treatment mimics short days, and also enhances rodent immune function. Reproductive responsiveness to melatonin appears to affect immune function. In sum, melatonin may be part of an integrative system to coordinate reproductive, immunologic, and other physiological processes to cope successfully with energetic stressors during winter.     

Molecular complementarity I: the complementarity theory of the origin and evolution of life

We assert that molecular complementarity is much more widespread than is commonly acknowledged in biological systems, if not actually ubiquitous. It creates the coupling necessary for non-equilibrium systems to form. It stabilizes aggregates against degradation, thereby increasing concentrations to levels adequate to foster the formation of prebiotic systems and represents the earliest form in which natural selection was manifested. Complementarity confers on all interacting parts of such systems in formation carrying capacity. RNA or DNA are not, therefore, necessary to the emergence of life, but represent specialized forms of complementary molecules adapted specifically to information storage and transmission. Non-genetic information exists in metabolic functions and probably preceded genetic information historically. Complementarity also provides the basis for homeostasis and buffering of such systems not only in a chemical, but also in structural and temporal terms. It provides a mechanism for understanding how new, emergent properties can arise, and a basis for the self-organization of systems. We demonstrate that such aggregates can have properties not predictable from their individual components, thus providing a means for understanding how new functions emerge during evolution. Selection is for modules rather than individual components. The formation of functional sub-systems that can then be integrated as modules greatly increases the probability of the emergence of life. The result of such modular evolution alters the standard view of evolution from a tree or bush-like image to an integrated network composed of alternating periods of integration (as molecules and molecular aggregates merge) and divergence (as molecules and aggregates undergo variations). This provides a mechanism for evolution by punctuated equilibria. Molecular complementarity puts strict limits on variations, however, preventing evolution from being random. The evolutionary, physiological and embryological consequences of this view of life are outlined, and various models and experiments described that further characterize it.     

The acute phase reaction syndrome: the acute phase reactants (a review)

The acute phase reaction of the organism, which determines the response that follows the injury of tissues and organs and helps the survival of the individual is reviewed. The main participants, the induction of the reaction and the regulatory mechanisms are shortly discussed, with special respect to the prominent role of interleukin-6. The relationship between the production and synthesis of the acute phase reactants under physiological and pathophysiological conditions is analyzed. The particular functions of orosomucoid and alpha 2HS-glycoprotein are summarized. Finally, the common biological actions of IL-6 and the acute phase reactants are mentioned.     

Momentous events and the life story.

Memories of specific life episodes, termed personal event memories, have only recently become a focus of systematic research. In this article, memories of momentous events are analyzed from a functional perspective. First, personal event memory is defined. Second, research on the temporal organization of specific memories across the life span is described. Third, psychological functions served by remembering momentous events are illustrated. Fourth, variations in the structure and content of autobiographical memory are identified. Finally, potential connections to clinical and educational practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exercise training in heart failure: inpatient and outpatient considerations

Highly reactive oxygen species that are formed during normal metabolism and under conditions of oxidative stress are able to oxidize proteins or convert lipid and carbohydrate derivatives to compounds that react with functional groups on proteins. Among other changes, these ROS-mediated reactions lead to the formation of protein carbonyl derivatives, which serves as a marker of ROS-mediated protein damage. On the basis of this marker, it is established that oxidatively damaged protein is associated with aging and some diseases. The accumulation of oxidatively damaged protein reflects the balance among a myriad of factors that govern the rates of ROS generation and the rate at which damaged protein is degraded. Peroxynitrite, which is formed under normal physiological conditions, is able to oxidize methionine residues in proteins and to nitrate tyrosine residues; however, its ability to do so is dependent on the availability of CO2, which stimulates the nitration of tyrosine residues but inhibits the oxidation of methionine residues. Nitration of tyrosine residues may contribute to peroxynitrite toxicity, as nitration precludes the phosphorylation or nucleotidylation of tyrosine residues and thereby seriously compromises one of the most important mechanisms of cellular regulation and signal transduction.     

Basic biomechanics of the spine

The purpose of this presentation is to provide basic biomechanical information concerning the spine, its components, and the spinal cord. It is shown that this information is helpful in understanding the fundamental functions of the spinal column. The experimentally determined physical properties of the vertebra, various spinal ligaments, the disc, and the spinal cord under many different loading conditions are described. The role of the special characteristics of the spine ligaments in allowing physiological motions of the spine, preventing excessive motions between vertebrae, and protecting the spinal cord during trauma are discussed. Movements of the spinal cord within the spinal canal and associated changes of its section during physiological movements of the spine are also described. The kinematics of the various regions of the spine are discussed and their clinical significance is presented. The problems of spinal trauma and is associated spinal instability are analyzed. Guidelines are recommended to assess spinal stability. The proper application of such guidelines will provide the basis for sound clinical judgments.     

Temporal variations in the pattern of breathing

Breath-to-breath variations in the pattern of breathing can occur as uncorrelated random variations ("white noise"), correlated random changes, or as one of two types of nonrandom variations: periodic oscillations or nonrandom nonperiodic fluctuations. White noise is probably present in all physiological processes. In many cases, periodic variations are due to oscillations originating in chemoreflex feedback loops. It has long been hypothesized that correlated random variations in breathing pattern are due to central neutral "memory" mechanisms, but part of this behavior might be due to chemoreflex mechanisms. Recently it has been concluded that nonlinear interactions between pulmonary and airway afferent activities and integrative central respiratory mechanisms can produce nonrandom nonperiodic (and also periodic) variability of the respiratory pattern. These latter studies have provided new insights about the behavioral relevance of the integrative character of central respiratory mechanisms and the time-varying nature of pulmonary afferent activities and have emphasized the importance of identifying the physiological bases for these phenomena. These and other findings are interpreted assuming that respiratory rhythm generation/pattern formation occurs via a nonlinear oscillator, and novel inferences concerning temporal variations of the breathing pattern are proposed.     

Success rate of cytogenetic analysis at the time of second-trimester dilation and evacuation

Hypoxia elicits a number of compensatory responses in animals, including behavioral hypothermia. The hypothesis that hypoglycemia induces hypothermia in the bullfrog Rana catesbeiana was tested and that this behavioral response would be beneficial. Frogs equipped with a temperature probe were tested in a thermal gradient (10-40 degrees C). Insulin (15 IU kg-1) caused significant reduction of body temperature, from 25.0 to 17.8 degrees C. A non-metabolizable glucose analogue, 2-deoxy-D-glucose (2-DG, 50 mg kg-1), which blocks intracellular glucose utilization, was also injected and caused a similar drop in body temperature, despite an increase in plasma glucose levels. To assess the possible benefits of hypoglycemia-induced hypothermia, the effects of insulin and 2-DG injections were measured on plasma glucose concentration and on oxygen consumption of frogs equilibrated at 10, 20 and 30 degrees C. The plasma glucose was elevated at higher temperatures and so was oxygen consumption. The insulin caused a significant reduction of plasma glucose concentration (about 1.22 muMol ml-1) whereas 2-DG caused a significant increase (about 0.70 muMol ml-1) at 30 degrees C. Both drugs caused a reduction of oxygen consumption (approximately 0.388 and 0.382 ml min-1 kg at 30 degrees C after insulin and 2-DG injection, respectively). No effect of either insulin or 2-DG was observed when the animals were equilibrated at 10 degrees C. In conclusion, hypothermia may be a beneficial response to hypoglycemia in frogs.     

Effects of mild (33 degrees C) and moderate (29 degrees C) hypothermia on cerebral blood flow and metabolism, lactate, and extracellular glutamate in experimental head injury

The effects of mild (33 degrees C) and moderate (29 degrees C) hypothermia were investigated to determine which temperature was more effective against compression-induced cerebral ischemia. Eighteen cats were anesthetized. The animals were divided into three groups according to deep-brain temperature (control, 37 degrees C; mild hypothermia, 33 degrees C; and moderate hypothermia, 29 degrees C). Intracranial pressure (ICP) and cerebral blood flow (CBF) were monitored, the latter by hydrogen clearance. Arteriovenous oxygen difference (AVDO2) and cerebral venous oxygen saturation (ScvO2) were measured in blood samples from the superior sagittal sinus. The cerebral metabolic rate of oxygen (CMRO2) and the cerebral metabolic rate of lactate (CMR lactate) were calculated. Extracellular glutamate was measured by microdialysis. ICP was increased by inflation of an epidural balloon until CBF became zero, and this ischemia was maintained for 5 min, after which the balloon was quickly deflated. All parameters were recorded over 6 h. Evans blue was injected to examine vascular permeability changes. CBF was decreased by 56% by mild hypothermia and by 77% by moderate hypothermia. Mild hypothermia had a coupled metabolic suppression whereas moderate hypothermia significantly increased AVDO2 and decreased ScvO2, producing a low CBF/CMRO2 (relative ischemia). After balloon deflation, all three groups showed reactive hyperemia, which was significantly reduced by mild and moderate hypothermia. CBF then decreased to 50% of pre-inflation values and ScvO2 decreased (post-ischemic hypoperfusion). CBF/CMRO2, ScvO2, and AVDO2 did not differ significantly between the three groups. After balloon deflation, all three groups showed increased CMR lactate, which was significantly reduced by mild and moderate hypothermia. Extracellular glutamate increased in control animals (3.8 +/- 1.72 microM), an effect most effectively suppressed in the mild hypothermia group (1.0 +/- 0.46 microM). Damaged tissue volumes as indicated by Evans blue dye extravasation were 729 +/- 89 mm3 in control, 247 +/- 56 mm3 in mild hypothermia, and 267 +/- 35 mm3 in moderate hypothermia animals. These data suggest that mild hypothermia (33 degrees C) might be the optimal brain temperature to treat compression-related cerebral ischemia.     

高疲劳寿命轴承钢洁净度现状及研究进展

对比了国内外高疲劳寿命轴承钢主要杂质元素、主要夹杂物特征等冶金性能的差异，并对比了不同冶金质量下，轴承钢的疲劳性能及诱发疲劳断裂的因素，总结了国产轴承钢洁净度现状及与国外优质轴承钢的差距。在此基础上，围绕高疲劳寿命轴承钢，以进一步提高国产轴承钢质量为目的，分析梳理了国产轴承钢冶炼技术及夹杂物控制方法的发展轨迹，探讨了国产轴承钢进一步提高疲劳寿命及质量的发展方向。      

Effects of growth hormone on neuroendocrine function

Although the role of growth hormone (GH) in the control of reproductive functions is not well understood, there is considerable evidence that the states of both GH deficiency and GH excess are typically associated with reproductive deficits. To identify the possible involvement of functional alterations in the hypothalamic-pituitary system in producing these deficits, we are studying neuroendocrine function related to reproduction in transgenic animals overexpressing GH, in animals with congenital GH deficiency, and in animals with selective immunoneutralization of GH. The results indicate that GH acts on the hypothalamus to alter dopaminergic and noradrenergic control of prolactin and gonadotropin release. Life-long elevation of GH levels outside the physiological ranges disrupts feedback control of luteinizing hormone (LH) release by gonadal streroids. Plasma LH and follicle-stimulating hormone (FSH) levels and feedback control of LH release are also abnormal in GH-deficient animals indicating that physiological levels of endogenous GH are normally involved in the control of gonadotropin release. Differences between the effects of bovine vs. human GH in transgenic mice and differential effects of GH deficiency in mice and rats should facilitate identification of the mechanisms involved in the actions of GH on the hypothalamic-pituitary system.     

Biochemical mechanisms of evolution and the role of oxygen

The concept formulated here presumes the existence of specific mechanisms of evolution that save intermediate (and therefore imperfect) forms of organisms from elimination by natural selection. A change in the life strategy made in situations when the appearance of a new trait worsens, rather than improves, adaptation of the organism to the changing environment can be one of these mechanisms. The concept postulates that, in such cases, K-strategy (relatively low rates of reproduction and activity in general but long life span) is replaced by r-strategy (high activity and reproduction but short life span). A decrease in the life span upon the K --> r transition is suggested to be an unavoidable consequence of an elevation of formation of toxic reactive oxygen species under conditions of increased rates of aerobic metabolism required for the increased life activity. The phenomenon of giantism of transgenic tobacco plants that overproduce a mitochondrial heat shock protein (experiments done by A. Moore) is assumed to be explained by an r --> K transition. On the other hand, a decrease in the life activity and a considerable increase in life span occurring in a nematode upon mutations inhibiting the CoQ biosynthesis (S. Hekimi) might serve as an example of a K --> r transition.     

The importance of time as stimulus of conditioned reflex activity.

"The formation of conditioned reflexes to time plays an important part in the systemic activity of the cerebral cortex, in the development of definite periodicity in physiological functions, and in the establishment of rhythmical pattern reactions in the working activity of man. By virtue thereof the question of the cortical mechanisms involved in the process of formation of conditioned reflexes to time acquires considerable theoretical and practical importance." Studies, from Russian laboratories, employing a variety of experimental animals, and man, are cited. Experimental variables are systematically described as well as the many theoretical issues. 34 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Muscarinic receptors involved in hippocampal plasticity

The cholinergic septohippocampal system has been associated with learning and memory, as evidenced by the severe loss of these functions in lesioned animals as well as in senile demented patients. In an attempt to comprehend the physiological basis of the cholinergic innervation for hippocampal functions, numerous studies employed the in-vitro hippocampal slice preparation and analyzed the consequences of exposing the cells to cholinergic ligands. Many effects of activating a cholinergic receptor in the hippocampus were thus described, including blockade of several types of potassium conductances, yet few of these effects are intuitively related to the involvement of the cholinergic system in hippocampal plasticity. An alternative approach involves focusing on the possible effect of low concentration of cholinergic ligands on reactivity of the hippocampus to afferent stimulation. We found two new actions of acetylcholine (ACh); The first one is a fast onset, short lived increase in cellular responses to activation of the N-methyl-D-aspartate (NMDA) receptor, and the second one is a slow onset, long lasting increase in reactivity to afferent stimulation, resembling that produced by a tetanic stimulation, which we called muscarinic long term potentiation (LTPm). The latter effect is mediated by a postsynaptic M2 receptor, and it shares several properties with the more familiar tetanic LTP. In addition, LTPm involves a rise of intracellular calcium concentration and an activation of both a tyrosine kinase and a serine/threonine kinase. Intuitively, LTPm is better related to hippocampal plasticity than the other reported effects of ACh in the hippocampus. Indeed, aged rats, which are cognitively impaired, lack LTPm while they do express other muscarinic actions. It is proposed that LTPm is an important link between the cholinergic action and function in the hippocampus.     

Surgical correction of acute congenital cardiopathies in the newborn infant

The experience of the Cardiac Surgery Service at the Hospital del Ni?o IMAN with the deep hypothermia method and hemodynamic arrest is shown in 30 infants with severe congenital cardiac malformations. The procedures followed before and during the operation are carefully described in their three aspects; anesthesia, extracorporeal circulation and surgery, including postoperative care. Ventilatory assistance is stressed. Results are analyzed considering postoperative evolution; stress is made on the causes of morbidity and mortality. Considering the results of this and other similar reports, we believe that the deep hypothermia method and heart arrest in treating severe cardiac malformations in infants are of outstanding importance since they have significantly improved results in these problems.     

A spin trap, N-tert-butyl-alpha-phenylnitrone extends the life span of mice

To characterize the pharmacological effects of N-tert-butyl-alpha-phenylnitrone (PBN) on life span, we administered PBN in drinking water to 24.5-month-old mice, and the survivors were counted. Their water consumption and body weights were measured as biological markers. PBN-treated animals as compared with control animals had prolonged mean and maximum life spans. Their water consumption decreased but no significant change was found in their body weights, indicating that the metabolism was improved. Results showed that PBN indeed affects physiological functions and extends life span. We propose that nitric oxide release from PBN may be involved in altering the aging process.     

Mice without myoglobin

Myoglobin, an intracellular haemoprotein expressed in the heart and oxidative skeletal myofibres of vertebrates, binds molecular oxygen and may facilitate oxygen transport from erythrocytes to mitochondria, thereby maintaining cellular respiration during periods of high physiological demand. Here we show, however, that mice without myoglobin, generated by gene-knockout technology, are fertile and exhibit normal exercise capacity and a normal ventilatory response to low oxygen levels (hypoxia). Heart and soleus muscles from these animals are depigmented, but function normally in standard assays of muscle performance in vitro across a range of work conditions and oxygen availability. These data show that myoglobin is not required to meet the metabolic requirements of pregnancy or exercise in a terrestrial mammal, and raise new questions about oxygen transport and metabolic regulation in working muscles.