Degradation of Polylactic Acid Using Sub-Critical Water for Compost.

Polylactic acid (PLA) is expected to replace many general-purpose plastics, especially those used for food packaging and agricultural mulch. In composting, the degradation speed of PLA is affected by the molecular weight, crystallinity, and microbial activity. PLA with a molecular weight of less than 10,000 has been reported to have higher decomposition rates than those with higher molecular weight. However, PLA degradation generates water-soluble products, including lactic acid, that decrease the pH of soil or compost. As acidification of soil or compost affects farm products, their pH should be controlled. Therefore, a method for determining suitable reaction conditions to achieve ideal decomposition products is necessary. This study aimed to determine suitable reaction conditions for generating preprocessed PLA with a molecular weight lower than 10,000 without producing water-soluble contents. To this end, we investigated the degradation of PLA using sub-critical water. The molecular weight and ratio of water-soluble contents (WSCs) affecting the pH of preprocessed products were evaluated through kinetic analysis, and crystallinity was analyzed through differential scanning calorimetry. Preprocessed PLA was prepared under the determined ideal conditions, and its characteristics in soil were observed. The results showed that the crystallization rate increased with PLA decomposition but remained lower than 30%. In addition, the pH of compost mixed with 40% of preprocessed PLA could be controlled within pH 5.4-5.5 over 90 days. Overall, soil mixed with the preprocessed PLA prepared under the determined ideal conditions remains suitable for plant growth.

Standard warfarin dose in a patient with the CYP2C9*3/*3 genotype leads to hematuria.

BACKGROUND: Patients with certain CYP2C9 genetic variants have increased sensitivity to warfarin and are at increased risk of over-coagulation with standard warfarin dose. We report over-anticoagulation and hematuria manifest as a slow increase in the international normalized ratio (INR) due to warfarin treatment in a patient with the CYP2C9*3/*3 allele. CASE: A 58-y-old man with paroxysmal atrial fibrillation received a standard warfarin dose of 2.0mg/day. Because INR was 2.00 one week after treatment initiation, he was discharged from the hospital. One month later, hematuria was present and INR had increased to 7.26. Although in normal cases (R)-warfarin plasma concentrations are higher than (S)-warfarin, this patient had the opposite warfarin enantiomer plasma concentration profile. CONCLUSIONS: Increased anticoagulation was due to an increased concentration of (S)-warfarin, the more active warfarin enantiomer. INR response to warfarin in this CYP2C9*3/*3 patient was slow. The later INR response appears to be strongly affected by CYP2C9 variants. He also had the VKORC1 -1639G>A AA genotype, requiring a lower warfarin dose. In this case, increased risk of bleeding could have been identified by prospective genotyping of CYP2C9 and VKORC1 prior to initiating warfarin therapy.

Atomic force microscopic studies on the structure of bovine femoral cortical bone at the collagen fibril-mineral level.

The structure of cortical bone at the collagen-mineral level was investigated by means of atomic force microscopy. Surfaces of the specimens treated with collagenase and ethylenediaminetetraacetic acid (EDTA) were examined. Images of blob-like objects observed in intact specimen became clearly outlined after collagenase treatment; the sizes of the blob decreased, suggesting that each blob had been fragmented by the collagenase treatment. Following EDTA treatment of an intact specimen, an image of thread-like objects appeared; the thread was partly constructed by trains of blobs and the other parts of the threads had a periodic pattern along its longer axis. The period was almost equal to the collagen D-period of the Hodge-Petruska model, indicating that the threads are collagen fibrils and that the blobs are related to the mineral phase in bone. It was concluded that minerals were deposited on and along collagen fibrils. A decorated collagen fibril model for the spatial relationship between mineral and collagen fibril was proposed. According to our model, the mineral inside the collagen fibril is about one forth of the extrafibrillar mineral.