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Severe Hypoxia (severe + hypoxia)

Distribution by Scientific Domains

Medical Sciences	58%
Life Sciences	33%

Selected Abstracts

Dural haemorrhage in non-traumatic infant deaths: does it explain the bleeding in ,shaken baby syndrome'?

NEUROPATHOLOGY & APPLIED NEUROBIOLOGY, Issue 1 2003
J. F. Geddes
J. F. Geddes, R. C. Tasker, A. K. Hackshaw, C. D. Nickols, G. G. W. Adams, H. L. Whitwell and I. Scheimberg (2003) Neuropathology and Applied Neurobiology 29, 14,22 Dural haemorrhage in non-traumatic infant deaths: does it explain the bleeding in ,shaken baby syndrome'? A histological review of dura mater taken from a post-mortem series of 50 paediatric cases aged up to 5 months revealed fresh bleeding in the dura in 36/50, the bleeding ranging from small perivascular haemorrhages to extensive haemorrhage which had ruptured onto the surface of the dura. Severe hypoxia had been documented clinically in 27 of the 36 cases (75%). In a similar review of three infants presenting with classical ,shaken baby syndrome', intradural haemorrhage was also found, in addition to subdural bleeding, and we believe that our findings may have relevance to the pathogenesis of some infantile subdural haemorrhage. Recent work has shown that, in a proportion of infants with fatal head injury, there is little traumatic brain damage and that the significant finding is craniocervical injury, which causes respiratory abnormalities, severe global hypoxia and brain swelling, with raised intracranial pressure. We propose that, in such infants, a combination of severe hypoxia, brain swelling and raised central venous pressure causes blood to leak from intracranial veins into the subdural space, and that the cause of the subdural bleeding in some cases of infant head injury is therefore not traumatic rupture of bridging veins, but a phenomenon of immaturity. Hypoxia with brain swelling would also account for retinal haemorrhages, and so provide a unified hypothesis for the clinical and neuropathological findings in cases of infant head injury, without impact or considerable force being necessary. [source]

Optical imaging of medullary ventral respiratory network during eupnea and gasping In situ

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006
Jeffrey T. Potts
Abstract In severe hypoxia, respiratory rhythm is shifted from an eupneic, ramp-like motor pattern to gasping characterized by a decrementing pattern of phrenic motor activity. However, it is not known whether hypoxia reconfigures the spatiotemporal organization of the central respiratory rhythm generator. Using the in situ arterially perfused juvenile rat preparation, we investigated whether the shift from eupnea to gasping was associated with a reconfiguration of the spatiotemporal pattern of respiratory neuronal activity in the ventral medullary respiratory network. Optical images of medullary respiratory network activity were obtained from male rats (4,6 weeks of age). Part of the medullary network was stained with a voltage-sensitive dye (di-2 ANEPEQ) centred both within, and adjacent to, the pre-Bötzinger complex (Pre-BötC). During eupnea, optical signals initially increased prior to the onset of phrenic activity and progressively intensified during the inspiratory phase peaking at the end of inspiration. During early expiration, fluorescence was also detected and slowly declined throughout this phase. In contrast, hypoxia shifted the respiratory motor pattern from eupnea to gasping and optical signals were restricted to inspiration only. Areas active during gasping showed fluorescence that was more intensive and covered a larger region of the rostral ventrolateral medulla compared to eupnea. Regions exhibiting peak inspiratory fluorescence did not coincide spatially during eupnea and gasping. Moreover, there was a recruitment of additional medullary regions during gasping that were not active during eupnea. These results provide novel evidence that the shift in respiratory motor pattern from eupnea to gasping appears to be associated with a reconfiguration of the central respiratory rhythm generator characterized by changes in its spatiotemporal organization. [source]

Behavioural responses of a south-east Australian floodplain fish community to gradual hypoxia

FRESHWATER BIOLOGY, Issue 3 2007
DALE G. MCNEIL
Summary 1. Hypoxic conditions occur frequently during hot, dry summers in the small lentic waterbodies (billabongs) that occur on the floodplains of the Murray-Darling River system of Australia. Behavioural responses to progressive hypoxia were examined for the native and introduced floodplain fish of the Ovens River, an unregulated tributary of the Murray River in south-east Australia. 2. Given the high frequency of hypoxic episodes in billabongs on the Ovens River floodplain, it was hypothesised that all species would exhibit behaviours that would confer a degree of hypoxia-tolerance. Specifically, it was hypothesised that as hypoxia progressed, gill ventilation rates (GVRs) would increase and aquatic surface respiration (ASR) would become increasingly frequent. Fish were subjected to rapid, progressive hypoxia from normoxia to anoxia in open tanks. 3. All tested species exhibited behaviours consistent with their use of potentially hypoxic habitats. As hypoxia progressed, GVRs increased and all species, with the exception of oriental weatherloach, began to switch increasingly to ASR with 90% of individuals using ASR at various oxygen concentrations below 1.0 mg O2 L,1. Australian smelt, redfin perch and flat-headed galaxias were the first three species to rise to ASR, with 10% of individuals using ASR by 2.55, 2.29 and 2.21 mg O2 L,1 respectively. Goldfish and common carp were the last two species to rise to ASR, with 10% of individuals using ASR by 0.84 and 0.75 mg O2 L,1 respectively. In contrast to other species, oriental weatherloach largely ceased gill ventilation and used air-gulping as their primary means of respiration during severe hypoxia and anoxia. 4. Australian smelt, redfin perch and flat-headed galaxias were unable to maintain ASR under severe hypoxia, and began exhibiting erratic movements, termed terminal avoidance behaviour, and loss of equilibrium. All other species continued to use ASR through severe hypoxia and into anoxia. Following a rise to ASR, GVRs either remained steady or decreased slightly indicating partial or significant relief from hypoxic stress for these hypoxia-tolerant species. 5. Behavioural responses to progressive hypoxia amongst the fish species of the Ovens River floodplain indicate a generally high level of tolerance to periodic hypoxia. However, species-specific variation in hypoxia-tolerance may have implications for community structure of billabong fish communities following hypoxic events. [source]

HIF-1 and p53: communication of transcription factors under hypoxia

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2004
Tobias Schmid
Abstract Oxygen sensing and reactivity to changes in the concentration of oxygen is a fundamental property of cell physiology. The lack of O2 (hypoxia) is transmitted into many adaptive responses, a process that is largely controlled by a transcription factor known as hypoxia inducible factor-1 (HIF-1). More recent reports suggest that besides its traditional regulation via proteasomal degradation other signaling pathways contribute to stability regulation of the HIF-1, subunit and/or HIF-1 transactivation. These regulatory circuits allow for the integration of HIF-1 into scenarios of cell-survival vs. cell-death with the rule of the thumb that short-term mild hypoxia maintains cell viability while prolonged and severe hypoxia provokes cell demise. Cell death pathways are associated with stabilization of the tumor suppressor p53, a response also seen under hypoxic conditions. Here we summarize recent information on accumulation of HIF-1, and p53 under hypoxia and provide a model to explain the communication between HIF-1 and p53 under (patho)physiological conditions. [source]

A major fish stranding caused by a natural hypoxic event in a shallow bay of the eastern South Pacific Ocean

JOURNAL OF FISH BIOLOGY, Issue 7 2010
E. Hernández-Miranda
A massive beaching and mortality of fishes occurred in Coliumo Bay, a shallow bay located along the coast of the eastern South Pacific Ocean on 3 January 2008. This stranding was a consequence of an abrupt decrease in the dissolved oxygen concentration throughout the whole water column, due to the effect of intense upwelling along the coast off central-southern Chile. The main objectives of this study were: (1) to characterize taxonomically and biologically the fish species assemblage present in this beaching; (2) to evaluate several physiological indicators for the condition of the beached species at the time of their death; and (3) to assess the possible cause,effect mechanisms involved in the fishes death and the changes that took place in the fish community throughout the time. In this beaching, 26 fish species were identified: 23 teleosts, one myxiniform and two elasmobranchs. Most beached specimens were juveniles. Haematological and histological evidence indicate that severe hypoxia that lasted for at least 48 h was the most plausible cause of death. The main conclusion of this study is that the presence of oxygen-poor equatorial sub-surface water in the shallow coastal zone due to intense regional-scale upwelling caused the fish stranding. Although the effect of the hypoxic event was severe for the fish assemblage of Coliumo Bay, the rapid recuperation observed suggests that hypoxic events at the local spatial scale can be buffered by migration processes from the fish community inhabiting close by areas non-affected by low oxygen conditions. The effect that severe hypoxic events may have on larger spatial scales remains unknown. [source]

The effect of oxygen tension on the in vitro assay of human osteoblastic connective tissue progenitor cells

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2008
Sandra M. Villarruel
Abstract Connective tissue progenitors (CTPs) are defined as the heterogeneous set of stem and progenitor cells that reside in native tissues and are capable of proliferation and differentiation into one or more connective tissue phenotypes. CTPs play important roles in tissue formation, repair, and remodeling. Therefore, in vitro assays of CTP prevalence and biological potential have important scientific and clinical relevance. This study evaluated oxygen tension as an important variable in optimizing in vitro conditions for quantitative assays of human CTPs. Bone marrow aspirates were collected from 20 human subjects and cultured using established medium conditions at ambient oxygen tensions of 1, 5, 10, and 20%. Colony-forming efficiency (CFE), proliferation, and colony density were assessed. CFE and proliferation were greatest at 5% O2. Traditional conditions using atmospheric oxygen tension (20% O2) reduced CFE by as much as 32%. CFE and proliferation at 1% O2 were less than 5% O2 but comparable to that seen at 20% O2, suggesting that CTPs are relatively resilient under hypoxic conditions, a fact that may be relevant to their function in wound repair and their potential use in tissue engineering applications involving transplantation into settings of moderate to severe hypoxia. These data demonstrate that optimization of quantitative assays for CTPs will require control of oxygen tension. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1390,1397, 2008 [source]

Dural haemorrhage in non-traumatic infant deaths: does it explain the bleeding in ,shaken baby syndrome'?

Two neonates with intussusception accompanying severe hypoxia

PEDIATRICS INTERNATIONAL, Issue 5 2005
Isao Ueki
No abstract is available for this article. [source]

Location and properties of respiratory neurones with putative intrinsic bursting properties in the rat in situ

THE JOURNAL OF PHYSIOLOGY, Issue 13 2009
Walter M. St.-John
Using the in situ arterially perfused preparations of both neonatal and juvenile rats, we provide the first description of the location, morphology and transmitter content of a population of respiratory neurones that retains a bursting behaviour after ionotropic receptor blockade. All burster neurones exhibited an inspiratory discharge during eupnoeic respiration. These neurones were predominantly glutamatergic, and were located within a region of the ventral respiratory column that encompasses the pre-Bötzinger complex and the more caudally located ventral respiratory group. Bursting behaviour was both voltage and persistent sodium current dependent and could be stimulated by sodium cyanide to activate this persistent sodium current. The population of burster neurones may overlap with that previously described in the neonatal slice in vitro. Based upon the present and previous findings, we hypothesize that this burster discharge may be released when the brain is subject to severe hypoxia or ischaemia, and that this burster discharge could underlie gasping. [source]

Head and Neck Cancer: The Importance of Oxygen ,

THE LARYNGOSCOPE, Issue 5 2000
David J. Terris MD
Abstract Objectives To use recently introduced polarographic technology to characterize the distribution of oxygenation in solid tumors, explore the differences between severe hypoxia and true necrosis, and evaluate the ability to predict treatment outcomes based on tumor oxygenation. Study Design Prospective, nonrandomized trial of patients with advanced head and neck cancer, conducted at an academic institution. Methods A total of 63 patients underwent polarographic oxygen measurements of their tumors. Experiment 1 was designed to determine whether a gradient of oxygenation exists within tumors by examining several series of measurements in each tumor. Experiment 2 was an analysis of the difference in data variance incurred when comparing oxygen measurements using oxygen electrodes of two different sizes. Experiment 3 compared the proportion of tumor necrosis to the proportion of very low (,2.5 mm Hg) polarographic oxygen measurements. Experiment 4 was designed to explore the correlation between oxygenation and treatment outcomes after nonsurgical management. Results No gradient of oxygenation was found within cervical lymph node metastases from head and neck squamous cell carcinomas (P > .9). Tumor measurements achieved with larger (17 ,m) electrodes displayed smaller variances than those obtained with smaller (12 ,m) electrodes, although this difference failed to reach statistical significance (P = .60). There was no correlation between tumor necrosis and the proportion of very low (,2.5 mm Hg) oxygen measurements. There was a nonsignificant trend toward poorer locoregional control and overall survival in hypoxic tumors. Conclusions Hypoxia exists within cervical lymph node metastases from head and neck squamous carcinomas, but the hypoxic regions are distributed essentially randomly. As expected, measurements of oxygen achieved with larger electrodes results in lowered variance, but with no change in overall tumor mean oxygen levels. Polarographic oxygen measurements are independent of tumor necrosis. Finally, oxygenation as an independent variable is incapable of predicting prognosis, probably reflecting the multifactorial nature of the biological behavior of head and neck cancers. [source]

Pandemic (H1N1) 2009 influenza: experience from the critical care unit

ANAESTHESIA, Issue 11 2009
M. Patel
Summary This case series details experience of critical care admissions with pandemic (H1N1) 2009 influenza from an intensive care unit in the West Midlands. We present four critically ill patients admitted with severe hypoxia. Two of the patients failed a trial of continuous positive airway pressure and all underwent controlled ventilation within 24 h of admission. Bilevel and high frequency oscillatory ventilation were the most useful modes. Our patients generally had one organ failure and were ventilator dependent for relatively short periods of time. Three of the patients made a full recovery and one required ongoing dialysis. We also discuss service planning and our response to the pandemic. We were well prepared with stocks of personal protective equipment but had to modify plans as the outbreak progressed. Our cases and discussion provide useful information for other intensive care units preparing for the predicted autumn surge of H1N1 cases. [source]

Tumor hypoxia: A target for selective cancer therapy

CANCER SCIENCE, Issue 12 2003
Shinae Kizaka-Kondoh
Tumor hypoxia has been considered to be a potential therapeutic problem because it renders solid tumors more resistant to sparsely ionizing radiation (IR) and chemotherapeutic drugs. Moreover, recent laboratory and clinical data have shown that tumor hypoxia is also associated with a more malignant phenotype and poor survival in patients suffering from various solid tumors. Therefore, selective targeting of hypoxic tumor cells has been explored, and since severe hypoxia (pO2<0.33%, 2.5 mmHg) does not occur in normal tissue, tumor hypoxia could be exploited for therapeutic advantage. However, the following three characteristics of hypoxic tumor regions present obstacles in targeting hypoxic cells. First, it is difficult to deliver a sufficient amount of drug to a region that is remote from blood vessels. Second, one must specifically target hypoxic tumor cells while sparing normal well-oxygenated tissue from damage. Finally, the severely hypoxic tumor cells to be attacked have often stopped dividing. Therefore, high delivery efficiency, high specificity and selective cytotoxicity are all necessary to target and combat hypoxic tumor cells. The current review describes progress on the biological aspects of tumor hypoxia and provides a compilation of the recent molecular approaches used to target hypoxic tumors. These approaches include our work with a unique hypoxia-targeting protein drug, TOP3, with which we have sought to address the above three difficulties. [source]