The detailed mechanisms that facilitate the heat tolerance of terrestrial cyanobacteria have not been completely elucidated, although several reports have revealed aspects of the heat tolerance mechanisms of several o...The detailed mechanisms that facilitate the heat tolerance of terrestrial cyanobacteria have not been completely elucidated, although several reports have revealed aspects of the heat tolerance mechanisms of several other organisms. The dormant cells, called akinetes, of the terrestrial cyanobacterium Nostoc sp. HK-01 can revive after dry heat exposure at 100℃ for more than 10 h. We investigated the compatible solutes that protect the biomolecules in Nostoc sp. HK-01 akinetes using colonies containing various proportions of akinetes. We extracted the intracellular substances from each colony with 80% ethanol, which we purified with a series of analytical columns and analyzed by high-performance liquid chromatography and liquid chromatography-electrospray ionization-mass spectrometry. The compatible solutes were screened for their ability to prevent protein aggregation upon heating using the model enzyme lactate dehydrogenase. We detected an accumulation of glucosylglycerol, betaine, and glycine in akinetes. In addition, we confirmed that betaine, glycine, sucrose, and trehalose contributed to the prevention of the protein aggregation. The levels of sucrose and glycine in the colonies were approximately 1000× higher than those of glucosylglycerol, betaine, or trehalose. Our results indicated that sucrose and glycine are the main compatible solutes in the hydrophilic fractions of the cell extracts of Nostoc sp. HK-01 akinetes.展开更多
Ⅰ. INTRODUCTIONAmong procaryotic phototrophic cyanobacteria, most filamental species with heterocysts differentiate into akinetes with hibernant and reproductive functions. Akinete differentiation is initiated during...Ⅰ. INTRODUCTIONAmong procaryotic phototrophic cyanobacteria, most filamental species with heterocysts differentiate into akinetes with hibernant and reproductive functions. Akinete differentiation is initiated during the late exponential phase of growth. It is believed that the formation of akinetes occurs under conditions unfavorable to growth and the internal structures of the akinete change remarkably in the course of differentiation. A great amount of in-展开更多
Rationale:Delayed post-hypoxic leukoencephalopathy(DPHL)is usually an overlooked condition,which arises as a result of a multitude of reversible and irreversible conditions.Patient’s Concern:A 50-year-old female with...Rationale:Delayed post-hypoxic leukoencephalopathy(DPHL)is usually an overlooked condition,which arises as a result of a multitude of reversible and irreversible conditions.Patient’s Concern:A 50-year-old female with a history of epilepsy,who developed DPHL 12 days after respiratory failure secondary to barbiturate toxicity.Diagnosis:DPHL on magnetic resonance imaging of the brain.Interventions:Mechanical ventilation was initiated for respiratory failure and hemodialysis for barbiturate toxicity.Outcomes:The patient developed akinetic mutism due to infirmity and had a residual disability,which led to permanent dependency.Lessons:The diagnosis of DPHL is often delayed or missed,given the rarity of this condition and its inconsistent clinical symptomatology.Diagnostic delay can be avoided by early recognition of the classical“delayed onset”symptoms.展开更多
文摘The detailed mechanisms that facilitate the heat tolerance of terrestrial cyanobacteria have not been completely elucidated, although several reports have revealed aspects of the heat tolerance mechanisms of several other organisms. The dormant cells, called akinetes, of the terrestrial cyanobacterium Nostoc sp. HK-01 can revive after dry heat exposure at 100℃ for more than 10 h. We investigated the compatible solutes that protect the biomolecules in Nostoc sp. HK-01 akinetes using colonies containing various proportions of akinetes. We extracted the intracellular substances from each colony with 80% ethanol, which we purified with a series of analytical columns and analyzed by high-performance liquid chromatography and liquid chromatography-electrospray ionization-mass spectrometry. The compatible solutes were screened for their ability to prevent protein aggregation upon heating using the model enzyme lactate dehydrogenase. We detected an accumulation of glucosylglycerol, betaine, and glycine in akinetes. In addition, we confirmed that betaine, glycine, sucrose, and trehalose contributed to the prevention of the protein aggregation. The levels of sucrose and glycine in the colonies were approximately 1000× higher than those of glucosylglycerol, betaine, or trehalose. Our results indicated that sucrose and glycine are the main compatible solutes in the hydrophilic fractions of the cell extracts of Nostoc sp. HK-01 akinetes.
文摘Ⅰ. INTRODUCTIONAmong procaryotic phototrophic cyanobacteria, most filamental species with heterocysts differentiate into akinetes with hibernant and reproductive functions. Akinete differentiation is initiated during the late exponential phase of growth. It is believed that the formation of akinetes occurs under conditions unfavorable to growth and the internal structures of the akinete change remarkably in the course of differentiation. A great amount of in-
文摘Rationale:Delayed post-hypoxic leukoencephalopathy(DPHL)is usually an overlooked condition,which arises as a result of a multitude of reversible and irreversible conditions.Patient’s Concern:A 50-year-old female with a history of epilepsy,who developed DPHL 12 days after respiratory failure secondary to barbiturate toxicity.Diagnosis:DPHL on magnetic resonance imaging of the brain.Interventions:Mechanical ventilation was initiated for respiratory failure and hemodialysis for barbiturate toxicity.Outcomes:The patient developed akinetic mutism due to infirmity and had a residual disability,which led to permanent dependency.Lessons:The diagnosis of DPHL is often delayed or missed,given the rarity of this condition and its inconsistent clinical symptomatology.Diagnostic delay can be avoided by early recognition of the classical“delayed onset”symptoms.
