About a correlation between calcium ion concentration (Ca2+) in the blood and the state of physiological functions in animals in deep cooling

The changes in physiological functions of the organism (respiration, functions of the heart and vessels, thermoregulation) were studied. The concentration of Ca2+ ions in the blood of white rats was determined by the ion-selective electrodes at various stages of hypothermia. The aim of the study was to reveal changes in the blood concentration of ionized calcium in animals during their gradual cooling. In deep hypothermia (16 degrees C), calcium ion concentration in the blood increased by 30% against the norm which coincides with arrest of the cold shivering and lung ventilation. An increased content of Ca2+ in the blood is supposed to result in an increase in the content of these ions in the intercellular liquid and in the nervous cells, which is one of the reasons for the cold paralysis of the respiration and thermoregulation centers.     

Ca(2+) level in the animal blood and their cold resistance

Administration of small doses of the EDTA decreased by 15-20% the Ca2+ contentn in the blood plasma of rabbits and rats. The decrease coincided with an abrupt stimulation of the thermoregulation system of cooled animals. Restoration of the Ca2+ content in circulating blood coincided in time with repeated suppression of the system's functions. The findings corroborate the theory of a key role of the Ca2+ in sensitivity of the homoiothermal organism to cold and substantiates the method of restoring physiological functions in deep hypothermia without rewarming the body.     

低温微生物及其酶类的研究概况

广泛分布在地球寒冷生境 ,如南北两极、高山、深海以及冰川中的低温微生物 ,不但为研究低温生态系统、生命起源与进化以及生物适冷机制提供了丰富的材料 ,同时在生物工程方面也具有潜在的巨大开发价值。国内外越来越多的科研人员对低温微生物及其产物的研究表现出了浓厚的兴趣。关于细胞膜和低温酶的研究 ,是目前微生物适冷机制研究中的 2个热点。就低温微生物的研究现状和适冷机制以及低温酶类的研究进行了综述。     

Therapeutic cold: An effective kind to modulate the oxidative damage resulting of a skeletal muscle contusion

Muscular contusions affect the function of the skeletal muscle system. This study investigated the oxidative damage as well as the main morphological changes related to a skeletal muscle contusion in the gastrocnemius muscle of rats and also the capacity of therapeutic cold to modulate these parameters. The therapeutic cold modulated the increase of oxidative stress markers and also modulated the reduction in the antioxidants levels in the injured muscle. In enzyme assays, therapeutic cold was also effective in normalizing the muscle Na(+)/K(+) and Ca(2+) ATPases, lactate dehydrogenase and myeloperoxidase activities. Similarly, the lesioned non-treated animals presented evident impairments in the mitochondrial functions and in the muscle morphology which were diminished by the cold treatment. The therapeutic cold was able to modulate the oxidative damage possibly by its capacity to limit the inflammatory response intensity, to attenuate the impairment of the mitochondrial function and also to preserve the skeletal muscle morphology.     

Quinone analogue irrecoverably paralyses the filarial parasites in vitro

2,3-Dimethoxy-5-methyl-1,4-benzoquinone (Q0), an analogue of ubiquinone, irreversibly paralyses the adult and microfilariae of the cattle filarial parasite Setaria digitata. The same concentration of Q0 that paralyses the microfilariae of S. digitata also paralyses the microfilariae of the human filarial parasite Wuchereria bancrofti within the same duration. Thus the experiments done in the model S. digitata system can well be extended to the human filarial system. A drug at the level of the quinone-centered energy generating system, perhaps an analogue of quinone like Q0, can inactivate the filarial parasites and may prove to be an effective drug to control filariasis.     

Reversible deep whole-body hypothermia in rats

The effect of deep hypothermia on the rat's organism was investigated without the use of hypercapnic hypoxia or administration of medicine. The possibility of resuscitation and rehabilitation of rats after deep hypothermia depending on different rate of heating have been also studied. It has been observed that the cardiac activity stopped at about 3 degrees C. We supposed that the extremely intensive heating and temperature rise of an organism were both limiting factors. We have discovered that the low intensity of heating was the next factor of limitation which was connected with the duration of clinical death. These experiments showed that the intensive cooling and heating (about 0.4 degrees C per min.) are the best for resuscitation and rehabilitation after deep hypothermia.     

Gtdap-1 and the role of autophagy during planarian regeneration and starvation

Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts.     

Control of mitochondrial integrity in ageing and disease

Various molecular and cellular pathways are active in eukaryotes to control the quality and integrity of mitochondria. These pathways are involved in keeping a ‘healthy’ population of this essential organelle during the lifetime of the organism. Quality control (QC) systems counteract processes that lead to organellar dysfunction manifesting as degenerative diseases and ageing. We discuss disease- and ageing-related pathways involved in mitochondrial QC: mtDNA repair and reorganization, regeneration of oxidized amino acids, refolding and degradation of severely damaged proteins, degradation of whole mitochondria by mitophagy and finally programmed cell death. The control of the integrity of mtDNA and regulation of its expression is essential to remodel single proteins as well as mitochondrial complexes that determine mitochondrial functions. The redundancy of components, such as proteases, and the hierarchies of the QC raise questions about crosstalk between systems and their precise regulation. The understanding of the underlying mechanisms on the genomic, proteomic, organellar and cellular levels holds the key for the development of interventions for mitochondrial dysfunctions, degenerative processes, ageing and age-related diseases resulting from impairments of mitochondria.     

Effect of growth temperature on membrane fatty acid composition and susceptibility to cold shock of Bacillus amyloliquefaciens.

We investigated the fatty acid composition of the membrane of Bacillus amyloliquefaciens grown at different temperatures. A decrease in growth temperature was accompanied by an increase in the ratio of branched- to straight-chain fatty acids and a marked increase in the level of unsaturation of branched-chain fatty acids. When cells of this organism grown at 30 degrees C were cold shocked, viability and ability to secrete extracellular protease were lost. Growth of this organism at lower temperatures or addition of Tween 80 to cells caused the critical temperature zone for cold shocking to be lowered significantly. These results suggest a direct correlation between membrane fluidity and the susceptibility to cold shock.     

Brain death and brain life: rethinking the connection

The connection between brain life and brain death is neither as simple nor as defensible as it might at first appear. The problem rests with the two dominant competing definitions of death:...the loss of that which is necessary for the organism to continue to function as a whole;....the loss of that which is essentially significant to the nature of the organism... If death is understood as the loss of that which is necessary for the continued functioning of the organism as whole, then the apparent symmetry breaks down. If...death could be understood as the loss of that which is essentially significant to the nature of the organism....consciousness, then the symmetry would hold. However, that definition of death is indefensible. Therefore...statements about the status of anencephalic infants and early human embryos based upon a connection between brain death and brain life are unfounded.     

The evolution of cell death programs as prerequisites of multicellularity

One of the hallmarks of multicellularity is that the individual cellular fate is sacrificed for the benefit of a higher order of life-the organism. The accidental death of cells in a multicellular organism results in swelling and membrane-rupture and inevitably spills cell contents into the surrounding tissue with deleterious effects for the organism. To avoid this form of necrotic death the cells of metazoans have developed complex self-destruction mechanisms, collectively called programmed cell death, which see to an orderly removal of superfluous cells. Since evolution never invents new genes but plays variations on old themes by DNA mutations, it is not surprising, that some of the genes involved in metazoan death pathways apparently have evolved from homologues in unicellular organisms, where they originally had different functions. Interestingly some unicellular protozoans have developed a primitive form of non-necrotic cell death themselves, which could mean that the idea of an altruistic death for the benefit of genetically identical cells predated the invention of multicellularity. The cell death pathways of protozoans, however, show no homology to those in metazoans, where several death pathways seem to have evolved in parallel. Mitochondria stands at the beginning of several death pathways and also determines, whether a cell has sufficient energy to complete a death program. However, the endosymbiotic bacterial ancestors of mitochondria are unlikely to have contributed to the recent mitochondrial death machinery and therefore, these components may derive from mutated eukaryotic precursors and might have invaded the respective mitochondrial compartments. Although there is no direct evidence, it seems that the prokaryotic-eukaryotic symbiosis created the space necessary for sophisticated death mechanisms on command, which in their distinct forms are major factors for the evolution of multicellular organisms.     

Noncanonical cell death programs in the nematode Caenorhabditis elegans

Genetic studies of the nematode Caenorhabditis elegans have uncovered four genes, egl-1 (BH3 only), ced-9 (Bcl-2 related), ced-4 (apoptosis protease activating factor-1), and ced-3 (caspase), which function in a linear pathway to promote developmental cell death in this organism. While this core pathway functions in many cells, recent studies suggest that additional regulators, acting on or in lieu of these core genes, can promote or inhibit the onset of cell death. Here, we discuss the evidence for these noncanonical mechanisms of C. elegans cell death control. We consider novel modes for regulating the core apoptosis genes, and describe a newly identified cell death pathway independent of all known C. elegans cell death genes. The existence of these noncanonical cell death programs suggests that organisms have evolved multiple ways to ensure appropriate cellular demise during development.     

Voices from beyond the grave: The impact of apoptosis on the microenvironment

Programmed cell death, in particular apoptosis, has vital functions in every healthy organism. In a highly regulated manner cells which are no longer needed or are harmful to the organism undergo suicide. More than just the mere elimination of a cell, apoptosis is increasingly being recognized performing important roles in cellular communication with the microenvironment. These interactions with surrounding cells can have various, and sometimes competing outcomes. Apoptotic cells can promote survival, proliferation and inflammation, but depending on the context also prevent survival and inflammation. In this review, we will summarize the emerging literature on how dying cells can transfer information to their neighbours, and which outcomes this communication has for the whole tissue.     

Exertion-induced fatigue and thermoregulation in the cold

Cold exposure facilitates body heat loss which can reduce body temperature, unless mitigated by enhanced heat conservation or increased heat production. When behavioral strategies inadequately defend body temperature, vasomotor and thermogenic responses are elicited, both of which are modulated if not mediated by sympathetic nervous activation. Both exercise and shivering increase metabolic heat production which helps offset body heat losses in the cold. However, exercise also increases peripheral blood flow, in turn facilitating heat loss, an effect that can persist for some time after exercise ceases. Whether exercise alleviates or exacerbates heat debt during cold exposure depends on the heat transfer coefficient of the environment, mode of activity and exercise intensity. Prolonged exhaustive exercise leading to energy substrate depletion could compromise maintenance of thermal balance in the cold simply by precluding continuation of further exercise and the associated thermogenesis. Hypoglycemia impairs shivering, but this appears to be centrally mediated, rather than a limitation to peripheral energy metabolism. Research is equivocal regarding the importance of muscle glycogen depletion in explaining shivering impairments. Recent research suggests that when acute exercise leads to fatigue without depleting energy stores, vasoconstrictor responses to cold are impaired, thus body heat conservation becomes degraded. Fatigue that was induced by chronic overexertion sustained over many weeks, appeared to delay the onset of shivering until body temperature fell lower than when subjects were rested, as well as impair vasoconstrictor responses. When heavy physical activity is coupled with underfeeding for prolonged periods, the resulting negative energy balance leads to loss of body mass, and the corresponding reduction in tissue insulation, in turn, compromises thermal balance by facilitating conductive transfer of body heat from core to shell. The possibility that impairments in thermoregulatory responses to cold associated with exertional fatigue are mediated by blunted sympathetic nervous responsiveness to cold is suggested by some experimental observations and merits further study.     

Functional analysis of the immunosenescence of the human B cell system: dissociation of normal activation and proliferation from impaired terminal differentiation into IgM immunoglobulin-secreting cells

The abilities of B cells from 24 young (mean 26 yr) and 24 elderly (mean 86 yr) humans to proliferate and differentiate into immunoglobulin-secreting cells (ISC) were investigated. Initial studies in young subjects demonstrated that a Staph protein A (SpA)-driven system could simultaneously assess the proliferative and differentiative capabilities of B cells resulting in IgM production. B cell proliferative responses were found to be partially T cell-dependent, whereas differentiation was absolutely T cell-dependent. Also, no significant differences could be detected in the abilities of nonproliferating allogeneic and autologous T cells to support B cell responsiveness. Although B cells from elderly subjects continuously exposed to SpA displayed proliferative responses equal to young subjects, the differentiation of B cells from elderly subjects into IgM ISC was markedly reduced as compared to young subjects. Analyses of results from co-culture experiments showed that the differentiation impairments of B cells from some elderly subjects could be partially corrected by allogeneic T cells from young subjects, whereas the impairments of others were more refractory. Moreover, T cells from elderly subjects were able to promote the differentiation of B cells from young subjects. Other experiments in elderly subjects showed that significant impairments of B and T cell functions rarely coexisted and that compensatory increases in B or T cell function were not evident. Thus, B cells from certain elderly humans have intrinsic impairments of differentiation required for optimal IgM production even though activation and proliferation remain normal in the presence of SpA. These impairments in differentiation are sometimes improved by T cells from young subjects, although in some elderly individuals, the differentiative impairments fail to be reversed.     

How an organism dies affects the fitness of its neighbors

Programmed cell death (PCD), a genetically regulated cell suicide program, is ubiquitous in the living world. In contrast to multicellular organisms, in which cells cooperate for the good of the organism, in unicells the cell is the organism and PCD presents a fundamental evolutionary problem. Why should an organism actively kill itself as opposed to dying in a nonprogrammed way? Proposed arguments vary from PCD in unicells being maladaptive to the assumption that it is an extreme form of altruism. To test whether PCD could be beneficial to nearby cells, we induced programmed and nonprogrammed death in the unicellular green alga Chlamydomonas reinhardtii. Cellular contents liberated during non-PCD are detrimental to others, while the contents released during PCD are beneficial. The number of cells in growing cultures was used to measure fitness. Thermostability studies revealed that the beneficial effect of the PCD supernatant most likely involves simple heat-stable biomolecules. Non-PCD supernatant contains heat-sensitive molecules like cellular proteases and chlorophyll. These data indicate that the mode of death affects the origin and maintenance of PCD. The way in which an organism dies can have beneficial or deleterious effects on the fitness of its neighbors.     

Chemically induced Drosophila melanogaster mutants with changes in brain structure

Neurodegenerative human diseases are caused by nerve cell death and anatomical changes in some brain regions. Molecular genetic studies of Drosophila showed that this organism can serve as a valuable test-system for conserved mechanisms underlying human nervous system disorders. Analysis of brain functions is possible when the mutants with disturbed functions are available. In this study, we have developed a unique collection of Drosophila melanogaster mutants with morphological and neurodegenerative changes in brain structure, which were induced by chemical mutagens.     

FOXO-independent suppression of programmed cell death by the PI3K/Akt signaling pathway in Drosophila

Signaling through the PI3K/Akt/FOXO pathway plays an important role in vertebrates in protecting cells from programmed cell death. PI3K and Akt have been similarly shown to be involved in survival signaling in the invertebrate model organism Drosophila. However, it is not known whether PI3K and Akt execute this function by controlling a pro-apoptotic activity of Drosophila FOXO. In this study, we show that elevated signaling through PI3K and Akt can prevent developmentally controlled death in the salivary glands of the fruit fly. We further show that Drosophila FOXO is not required for normal salivary gland death and that the rescue of salivary gland death by PI3K occurs independent of FOXO. These results give support to the notion that FOXOs have acquired pro-apoptotic functions after separation of the vertebrate and invertebrate lineages.     

Gtdap-1 and the Role of Autophagy During Planarian Regeneration and Starvation

Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts.

Addendum to:

Gtdap-1 Promotes Autophagy and is Required for Planarian Remodeling During Regeneration and Starvation

C. González-Estévez, D.A. Felix, A.A. Aboobaker and E. Saló

Proc Natl Acad Sci USA 2007; 104:13373-8