Localized Anoxia Research Articles

Microscale advection governs microbial growth and oxygen consumption in macroporous aggregates.

Most microbial life on Earth is found in localized microenvironments that collectively exert a crucial role in maintaining ecosystem health and influencing global biogeochemical cycles. In many habitats such as biofilms in aquatic systems, bacterial flocs in activated sludge, periphyton mats, or particles sinking in the ocean, these microenvironments experience sporadic or continuous flow. Depending on their microscale structure, pores and channels through the microenvironments permit localized flow that shifts the relative importance of diffusive and advective mass transport. How this flow alters nutrient supply, facilitates waste removal, drives the emergence of different microbial niches, and impacts the overall function of the microenvironments remains unclear. Here, we quantify how pores through microenvironments that permit flow can elevate nutrient supply to the resident bacterial community using a microfluidic experimental system and gain further insights from coupled population-based and computational fluid dynamics simulations. We find that the microscale structure determines the relative contribution of advection vs diffusion, and even a modest flow through a pore in the range of 10 µm s-1 can increase the carrying capacity of a microenvironment by 10%. Recognizing the fundamental role that microbial hotspots play in the Earth system, developing frameworks that predict how their heterogeneous morphology and potential interstitial flows change microbial function and collectively alter global scale fluxes is critical.IMPORTANCEMicrobial life is a key driver of global biogeochemical cycles. Similar to the distribution of humans on Earth, they are often not homogeneously distributed in nature but occur in dense clusters that resemble microbial cities. Within and around these clusters, diffusion is often assumed as the sole mass-transfer process that dictates nutrient supply and waste removal. In many natural and engineered systems such as biofilms in aquatic environments, aggregates in bioremediation, or flocs in wastewater treatment plants, these clusters are exposed to flow that elevates mass transfer, a process that is often overlooked. In this study, we show that advective fluxes can increase the local growth of bacteria in a single microenvironment by up to 50% and shape their metabolism by disrupting localized anoxia or supplying nutrients at different rates. Collectively, advection-enhanced mass transport may thus regulate important biogeochemical transformations in both natural and engineered environments.

Rare earth elements and carbon isotope geochemistry of the Doushantuo Formation in South China: Implication for middle Ediacaran shallow marine redox conditions

The middle Ediacaran Shuram excursion, the largest negative δ13Ccarb excursion in Earth history, has been interpreted as indirect evidence for episodic oxidation and remineralization of deep ocean DOC (dissolved organic carbon). It has been hypothesized that such oxidation event may have occurred when anoxic DOC-laden deep water was brought to shallow shelves during oceanic upwelling, which is expected to cause localized anoxia in shallow environments. To test this prediction, we systematically analyzed rare earth elements (REE) and δ13Ccarb of the upper Doushantuo Formation carbonates in the Yangtze Gorges area of South China, which were deposited in an inner shelf environment and record a large negative δ13Ccarb excursion correlated to the Shuram event. The REE data show a significant positive shift in Ce/Ce* values, synchronous with a pronounced negative δ13Ccarb shift. This positive Ce/Ce* shift is interpreted to represent an oceanic anoxia event in shallow shelf environments, which may have been caused by the upwelling or impingement of oxygen-depleted and 12C-enriched deep water onto shelves. This anoxia event coincides with a sharp decline in the abundance and diversity of Ediacaran acanthomorphic acritarchs, raising the possibility that these two geobiological events may be causally related.

Reserve Utilization in Seeds of Arabidopsis thaliana Germinating in Microgravity

Seed reserve lipid utilization in Arabidopsis thaliana (L.) Heynh., ecotype Landsberg erecta, is delayed when germination takes place in microgravity; the cotyledon symplast lipid volume fraction is less than 7% in controls, whereas in microgravity samples over 15% of the symplast volume is lipid. Growth rate in the root is reduced in microgravity. These effects are interpreted as probably being the result of localized anoxia in the absence of atmospheric convection and mixing in the sealed growth chambers used.

Hippocampus and Epilepsy Surgery

Summary: Sclerosis of the cornu Ammonis, or Ammon's horn sclerosis (AHS), is an “often‐described, yet hitherto enigmatic phenomen,” as Spielmeyer described it in 1927. It has been detected in cases with ischemia, anoxia, or hypoglycemia and in more than half of the epileptic brains examined postmortem. Various theories about its pathogenesis have been propounded. Among them, the “Pathoklise” theory of the Vogts and the vascular theory of Spielmeyer et al. had prevailed until recently. In 1953, two articles were published to contribute to the pathogenesis of ictal automatism (a type of complex partial or temporal lobe seizure). One is the incisural sclerosis theory of Penfield et al., and the other is the AHS theory of Sano and Malamud. The former researchers described a diffuse sclerosis of the inferomesial temporal structures without, however, specifically relating it to AHS. They considered it to be the result of localized anoxia of that portion of the brain caused by incisural herniation occurring during parturition. Sano and Malamud maintained that AHS is a result of convulsions, a distinct scar adjacent to which epileptogenic foci may develop in the course of time to cause ictal automatism. The latter theory was corroborated by Sano, Falconer, and other investigators. Falconer expanded the theory to the assertion that not only ictal automatism but other types of intractable epilepsy may be due to “mesial temporal (Ammon's horn) sclerosis.” The most recent development in the pathogenesis of AHS is the excito‐toxicity theory, i.e., that AHS is caused by excessive excitation of neurons, probably by putative excitatory neurotransmitters, especially glutamate. For this theory, there is a significant body of evidence. Recent developments in glial physiology suggest that the existence of gliosis itself may actively exert a great influence on neurons so that neurons generate high‐frequency synchronous discharges as epileptogenic foci.

Encéphalopathies postanoxiques

Ischaemic brain damage can follow global cerebral hypoxia, localized cerebral hypoxia and global cerebral anoxia as it occurs after circulatory arrest. The calcium-ion-mediated mechanism is one of the main routes to cerebral deterioration. Barbiturates are restricted for treatment of increased intracranial pressure and seizures. Calcium channel blockers cannot yet be recommended. Therapy remains mainly symptomatic. Hyperglycaemia should be avoided.

Ammon's Horn Sclerosis

Sclerosis of the cornu Ammonis or Ammon's horn sclerosis (AHS) is an "often-described, yet hitherto enigmatic phenomena" as Spielmyer put it in 1927. It has been found in cases with ischemia, anoxia or hypoglycemia and in more than half of the epileptic brains examined at autopsy. Various theories about its pathogenesis have been propounded. Among them, the "Pathoklise" theory of the Vogts and the vascular theory of Spielmeyer and his associates were prevailing until recently. In 1953, two articles were published to contribute to the pathogenesis of ictal automatism (a type of complex partial or temporal lobe seizures). One is the incisural sclerosis theory by Penfield and his associates and the other is the Ammon's horn sclerosis theory by Sano and Malamud. The former authors described a diffuse sclerosis of the infero-mesial temporal structures without, however, specifically relating it to AHS. They considered it was the result of localized anoxia of that portion of the brain caused by incisural herniation occurring during parturition. Sano and Malamud maintained that AHS is a result of convulsions, a distinct scar adjacent to which epileptogenic foci may develop in the course of time to cause ictal automatism. The latter theory was corroborated by Sano, Falconer and others. Falconer expanded the theory to the assertion that not only ictal automatism but other types of intractable epilepsy may be due to "mesial temporal (Ammon's horn) sclerosis". The most recent development in the pathogenesis of AHS is the excitotoxicity theory. Namely, AHS is caused by excessive excitation of neurons, probably by putative excitatory neurotransmitters, especially, glutamate. For this theory, there is a significant body of evidence. The problem of AHS, an old research subject and a matter of long-lasting controversy, has now been updated and become one of the newest topics in the field of experimental neurobiology.

Ion uptake and respiration of dry bean roots subjected to localized anoxia

Ion uptake by dry bean root systems was examined during a three day treatment period. Three aeration treatments were applied to split root systems where both halves were aerated, both halves were nonaerated and one half aerated and the remaining half nonaerated (localized anoxia). Ion absorption was similar for the aerated control and localized anoxia treatments. The nonaerated control absorbed 2, 40, and 60 percent of the aerated control for K+, Ca++, and NO3−, respectively. Ion absorption by stressed plants appeared to increase directly with root growth in the aerated portions of the localized anoxia treatments. Localized anoxia resulted in greater potassium ion uptake per unit root weight and in greater root respiration rates of the aerated half of the Pinto III cultivar root system. Transpiration rates of Seafarer subjected to localized anoxia were 135% of the aerated control. The additional water use may have contributed to greater ion uptake, by mass flow, in the nonaerated portion of the localized anoxia treatment. Nutrient solutions of the nonaerated controls became more alkaline during stress than did the nonaerated portions of the localized anoxia treatments, indicating a possible direct or indirect effect of the aerated portions of the localized anoxia treatments on the corresponding nonaerated half. Compensation in ion uptake by dry bean roots subjected to localized anoxia appeared to be the result of increased root growth, greater respiration rates, greater transpiration rates and, for Pinto III, an increase in the ion uptake rate per unit root weight. This compensatory uptake of water and nutrients by the root system may be one mechanism by which roots overcome localized stress within a soil profile.

Carbon Transport and Root Respiration of Split Root Systems of Phaseolus vulgaris Subjected to Short Term Localized Anoxia

The influence of anoxia on carbon transport and root respiration was evaluated by applying [U-(14)C]sucrose to the foliage. Translocation patterns to the root systems of two dry edible bean genotypes (Phaseolus vulgaris L.) were examined after a 3-day exposure to aerated and nonaerated environments. Localized anoxia of root systems was simulated by growing roots in split configurations and exposing half of the system to anoxic conditions. Anoxia of the root system for 72 hours reduced the movement of (14)C label into the roots with concurrent accumulations in the hypocotyl region. The translocation of (14)C label to anoxic roots was less than 50% of the aerated controls of both genotypes. Most of the (14)C label translocated to anoxic root systems was excluded from respiratory metabolism during the 3-hour pulse/chase period and was an order of magnitude less than the aerated controls. These observations suggest that the bulk of (14)C label which entered the root during the anoxic period was unavailable for metabolism by the enzymes of glycolysis and/or was diluted by a relatively large metabolite pool. A higher percentage of (14)C label was translocated to the aerated half of the localized anoxia treatment relative to the half of the aerated controls. The proportion of (14)C label translocated to the root system in the aerated control was 20 and 16% compared to 28 and 25% in the aerated localized anoxia treatment for the genotypes Seafarer and line 31908, respectively. Line 31908 partitioned a greater percentage of (14)C-labeled compounds to the actively growing fraction of the root system in the localized anoxia treatment than did Seafarer. This suggests a greater reliance on previously stored carbohydrate for immediate root growth in Seafarer than in line 31908.

Sedimentology and Ichnology of the Cretaceous-Tertiary Boundary in Denmark: Implications for the Causes of the Terminal Cretaceous Extinction

ABSTRACT Trace fossils and other sedimentologic evidence of bioturbation in latest Cretaceous and earliest Tertiary marine deposits in Denmark provide important clues to understanding the ecology of the sea bottom immediately before, during, and after the terminal Cretaceous boundary event. Trace-fossil associations at all the onshore Danish boundary sites indicate a general upward shoaling of the late Maastrichtian chalk sea, which was accompanied by an abrupt shift from a carbonate ooze sea floor to a marly, clay-rich, unstable substrate at the boundary. Although the substrate condition may have become more stable in the early Danian, water depths never did return to their former deep level. There is evidence of localized anoxia during the deposition of some boundary sediments (in the Fish Clay) in shallow parts of the Danish Maastrichtian sea, but no clear evidence of anaerobic conditions occurring at the era boundary was observed in boundary strata deposited in deeper water near the center of the basin. In fact, earliest Danian marl there is totally bioturbated. A pulse of calcite dissolution in shallow water coincided precisely with the era boundary, and this event played a major role in the formation of the Fish Clay in eastern Denmark, which is a condensed series of smectitic clay-rich layers from which much calcite has dissolved. The effects of this dissolution episode, however, were not so extreme in the marl that was deposited at the same time in slightly deeper water in northwestern Denmark. Evidence from Cretaceous-Tertiary boundary sequences in Denmark and elsewhere suggests that no single catastrophe can account for the major biotic extinctions that occurred at the end of the Cretaceous Period. The primary causal factors of the terminal Cretaceous extinction event appear to be drastic global sea-level regression occurring simultaneously with extensive volcanism on land and a strong pulse of calcite dissolution in ocean surface waters.

蜘蛛膜下腔播種性転移を認めた橋膠腫の1剖検例

An autopsy case of pontine astrocytoma with extensive subarachnoid dissemination was presented. The patient was a girl of 12 years old, who was admitted to the hospital because of decreased visual acuity and double vision. CT examination of the brain showed the findings consistent with neoplastic enlargement of the pons. Irradiation and immunotherapy afforded partial remission and she discharged 2 months after admission. Her symptoms, however, recurred 3 months after discharge and CT examination revealed obstructive hydrocephalus. Construction of ventriculo-peritoneal shunt afforded temporary reduction of her symptoms, but decerebrated posture appeared and her general condition progressively deteriorated. The patient died 1 year and 6 months after the onset of her initial symptoms.Autopsy revealed diffuse neoplastic enlargement of th e pons and extensive dissemination of tumor tissue in the subarachnoid space over the cerebral ventral surface and cerebellopontine angles. Superficial cortical tissue adjacent to subarachnoid dissemination was found to be invaded secondarily by tumor tissue.Histologically tumor in the pons showed the feature of well differentiated fibrillary astrocytoma with abundant production of glial fibrils. Cellular atypism was not prominent and mitotic figures were rare, but flowcytometric analysis of DNA distribution of this tumor showed an increase of tetraploid cells, suggesting malignancy.Disseminated foci in subarachnoid spa ce showed highly cellular neoplasm composed of smallsized cells, which was reminiscent of medulloblastoma. Mitotic figures were abundant. Transitional features to fibrillary astrocytoma were apparent and intercellular deposition of acid mucopolysaccharides was seen in some areas. Reactive proliferation of vascular endothelial cells was prominent in subarachnoid tumor tissue. Deposition of tumor cells on the ependymal surface and secondary invasion into deep brain tissue was also noted.Reports of astrocytoma in the brain stem with subarachnoid dissemination are rare. Rarer are the cases similar to ours in which disseminated foci in subarachnoid space were composed mainly of small anaplastic cells, while primary site in the brain stem showed the features of well differentiated fibrillary astrocytoma. Similar cases were reported by Friede et al. (1982) and designated by them as “infantile small cell glioma”. Our case and their cases suggest that small cells in astrocytomas represent highly malignant characteristics and are liable to spread diffusely in the subarachnoid space.The significance of intercellu lar deposition of acid mucopolysaccharides in astrocytomas was also discussed. It was suggested that localized anoxia due to inappropriate vascular supply caused an increase of permeability of the vascular wall which resulted in the deposition of acid mucopolysaccharides in intercellular space.

Centrilobular injury following hypoxia in isolated, perfused rat liver.

Hypoxia was produced in isolated, hemoglobin-free, perfused rat liver by reducing the flow rate of oxygen-carrying fluid entering the organ. The procedure caused anoxia in centrilobular regions. In these anoxic areas, structural derangements developed rapidly, characterized by bleb-like protrusions of hepatocyte plasma membrane through fenestrations in the sinusoidal endothelium. Periportal tissue remained normoxic and was completely spared. Cellular injury resulting from localized anoxia may play an important role in the pathogenesis of centrilobular liver disease.

The chemical basis for the intolerance of the brain to anoxia.

SUMMARYNervous tissue depends on oxygen consumption because the anaerobic formation of energy‐rich intermediates is insufficient for obligatory metabolic needs. The enzyme activities, and therefore the metabolic pathways, are unable to be adjusted to anoxia with sufficient rapidity. The effects of anoxia are probably more pronounced in certain cells or brain structures than in others. Overall chemical changes of the brain will therefore not necessarily disclose the crucial lesion in localized anoxia.

Pathogenesis of ventricular fibrillation in coronary occlusion. Perfusion of coronary arteries with serum.

THERE IS a great deal of evidence suggesting that the most frequent mechanism of death in coronary occlusion is by ventricular fibrillation. Very often this fatal complication may occur following small infarcts which apart from the acute arrhythmia, would have permitted survival with adequate myocardial function. A number of investigators have observed that a larger incidence of ventricular fibrillation occurs in the first 5-20 minutes following the production of the occlusion; thereafter the incidence decreases considerably. Although the pathogenesis of the ventricular fibrillation in coronary occlusion is not completely understood, it is believed that early and late fibrillation differ in the mechanism of their production. This study was carried out to ascertain the role of localized anoxia as a trigger mechanism in early ventricular fibrillation following coronary artery occlusion.For this purpose the artery distal to the occlusion was perfused with a nonoxygenated medium in order to eliminate the stasis which