Yeast cells were inactivated by carbon dioxide a t subcritical and supercritical temperatures over the pressure range of 1OOO-3OOO psi. A static apparatus was developed for the experiments. The results showed that a maximum of 15 min, depending on the pressure, was sufficient to inactivate yeast cells by 107-fold under supercritical conditions. Subcritical carbon dioxide was found to be much less effective. It took 30-40 min t o achieve inactivation of 104-fold and more than 1 h to achieve inactivation of 107-fold. There are two distinct mechanisms in the deactivation of yeast cells. The rate of cell inactivation is slow at first and increases drastically a t the later stage, suggesting that the penetration of CO2 into microbial cells was a primary controlling factor of the inactivation process. The inactivation rate was enhanced remarkably by a series of pressure release/recompression of C02 in the midst of a complete experiment. Other methods to improve the efficiency of inactivation are discussed.

Long-term morbidities can develop after traumatic brain injury (TBI). Some studies have suggested that the risk of stroke is higher after TBI, but the association between concussion and stroke remains unclear. Using a national cohort, the authors analyzed the incidence of both hemorrhagic and ischemic strokes in patients with previous concussion. A representative cohort of approximately one million people was followed up for four years. Patients with new-onset concussion were identified (n = 13,652) as the concussion group. Subsequently, the incidence rates of later stroke events in the concussion group were compared to a sex-, age- and propensity score–matched comparison group (n = 13,652). The overall incidence rate of stroke in the concussion group was higher than that of the comparison group (9.63 versus 6.52 per 1000 person-years, p < 0.001). Significantly higher stroke risk was observed in the concussion group than in the comparison group (crude hazard ratio 1.48, p < 0.001; adjusted HR 1.65, p < 0.001). In the concussion group, the cumulative incidence rates of both ischemic stroke and hemorrhagic stroke were higher than those of the comparison group (8.9% vs. 5.8% and 2.7% vs. 1.6%, respectively, both p < 0.001). Concussion is an independent risk factor for both ischemic and hemorrhagic strokes. Prevention and monitoring strategies of stroke are therefore suggested for patients who have experienced concussion.

Disruption of microbial cells by pressurized carbon dioxide at both subcritical and supercritical temperatures has been previously investigated. This method differs in principle from other disruption techniques and was found to have potential applications for rupture of a variety of microorganisms. However, it is not as effective for some of the microbial cells, including yeast, of which the cell walls are extremely robust and rigid. This work suggests an alternative operation to improve the disruption rates of cells by repeatedly releasing the applied fluid pressure within the cells in the midst of a disruption process. The improvement is substantial at all the experimental conditions studied.

Disruption of yeast cells with high‐pressure carbon dioxide at both subcritical and supercritical temperatures (25, 35, and 55 °C) was investigated. The experimental results revealed that yeast cells can be ruptured to a maximal level by carbon dioxide within 5 h at 5000 psi and 15 h at 1000 psi at any of the temperatures studied. In the presence of β‐glucuronidase, the length of time for maximal cell rupture was reduced to 90 min at 5000 psi. Off‐flavors of the ruptured yeast cells were removed by carbon dioxide in the process. The functional properties of proteins were preserved, as indicated by enzyme activities in the ruptured cell suspension. An increase in temperature from subcritical to supercritical of carbon dioxide led to a significant enhancement of rapture rates under high pressures, while the functional properties of proteins and the removal of off‐flavors were relatively insensitive to the variation of temperature if the process was maintained at or below 35 °C. At higher temperatures, the activities of enzymes began to decay and were lost at about 55 °C under the carbon dioxide pressures of this study.