誤嚥性肺炎予防に関する基礎研究 －核医学法による胃排出時間と体位の検討－

　老年者や脳卒中回復期にある患者にとって，誤嚥は死に至る肺炎の原因のひとつとして重要な課題である．とくに胃内容物は化学物質とともに感染物質を含んでおり，その誤嚥は重大な肺炎を引き起こす．胃食道逆流は，下部食道括約部の弛緩及び収縮不全が原因で，誤嚥性肺炎に導く重要な要素である．胃食道逆流の外的要因として摂食時，後の体位との関連も指摘され胃内容物の排出時間が重要と考えられている．そこで本研究ではこれらの患者の誤嚥性肺炎を予防するために，流動食の胃内容物の早期排出に着目し，食後の体位のなかで特に臨床的に多く観察される半座位について，胃排出時間と体位との関連を明らかにすることを目的に，健常者を対象に核医学検査を用いて基礎的検討を行った．核医学検査法は，半減期の短いアイソトープを食物と混合して経口投与し，ガンマカメラを用いて経時的に腹部を撮影することにより，胃からの放射能の減少部を定量的に評価して胃排出時間を測定する検査方法である．健康成人女性3人，平均年齢36.8歳を対象に，レトルト食品の白粥，250gにアイソトープ（99ｍTｃ-0 04,185KBq）を混入した検査食を用いて，それぞれ座位，半座位，仰臥位となり，60 分間観察した．結果，体位別の胃排出時間は，食物摂取後15 分頃までは体位による排出量に違いはなく，20 分後から違いが生じ，仰臥位・座位が60分程度で80%以上が排出されるのに対して，半在位では60分間で約60%の排出と，仰臥位と座位よりも停滞時間が長かったが，コンスタントに胃内容物が排出されていた．従って，誤嚥の予防はもちろんであるが，消化吸収の観点からも半座位が効果的な体位ではないかと考えられた．今回の検査では被験者数が少なく，検査食により胃排出時間は異なることや排泄など生活習慣の影響も予測されることから，今後多数例の検討を行う必要がある．For elderly persons or post-apoplectic patients during convalescence, aspiration as one of the causes of fatal pneumonia is important problem. The gastric contents in particular include infective materials as well as chemical substances, therefore aspiration of them induces serious pneumonia. Gastroesophageal reflux due to failure of the lower esophageal sphincter relaxation and contraction is an important element to lead to aspiration pneumonia. Also the association with the posture during and after eating is noted as an external factor of gastroesophageal reflux. We focused on early evacuation of gastric contents (fluid food) to prevent these patients from aspiration pneumonia. To reveal the relation between gastric emptying time and posture, we fundamentally examined postprandial posture, in particular semi-sitting position often observed clinically, in healthy subjects by nuclear medicine examination. In this examination, food mixed with isotope with short half-time was administered orally to the subjects. After that we evaluated the gastric radioactivity decrement quantitatively and measure gastric emptying time by acquiring the images of the abdomen using gamma camera over time, which allowed us to follow-up in vivo normal post-prandial kinetics. Although the institution capable of performing radioisotope method is limited, we used it because it was the most effective method to evaluate gastrointestinal motility precisely. The gastric emptying time for food (100% rice gruel) varied depending on the posture. The results of time in the supine and sitting position were shorter than that in the semi-sitting position and the food was evacuated constantly in the semi-sitting position. The study suggested that it was needed to maintain a posture for more than one hour. Since the gastric emptying time is also affected by the test food type, it is necessary that we should apply various quality and form foods in many cases to raise reliability

Embeddings for Non-Critical Superstrings

It was previously shown that at critical central charge, $N$-extended superstrings can be embedded in $(N+1)$-extended superstrings. In other words, $(N=0,c=26)\to (N=1,c=15)\to (N=2,c=6)\to (N=3,c=0) \to (N=4,c=0)$. In this paper, we show that similar embeddings are also possible for $N$-extended superstrings at non-critical central charge. For any $x$, the embedding is $(N=0,c=26+x) \to (N=1,c=15+x) \to (N=2,c=6+x) \to (N=3,c=x) \to (N=4,c=x)$. As was conjectured by Vafa, the $(N=2,c=9) \to (N=3,c=3)$ embedding can be used to prove that $N=0$ topological strings are special vaccua of N=1 topological strings.Comment: 8 pages latex, KCL-TH-94-6 and OU-HET 18

Toward the Universal Theory of Strings

We show that the $N=2$ superstrings may be viewed as a special class of the $N=4$ superstrings and demonstrate their equivalence. This allows us to realize all known string theories based on linear algebras and with $N<4$ supersymmetries as special choices of the vacua in the $N=4$ superstring.Comment: Latex file, 8 pages, NBI-HET-94-08. The preprint number is changed and one reference is adde

Note on W3 Realizations of the Bosonic String

In order to investigate to what extent string theories are different vacua of a general string theory (the ``universal string"), we discuss realizations of the bosonic string as particular background of certain types of $W$-strings. Our discussions include linearized $W_3^{lin}$, non-critical $W_3$, linearized $W_3^{(2)lin}$ and critical $W_3^{(2)}$ realizations of the bosonic string.Comment: 9 pages, Late

Physicochemical and immunological properties of the hepatitis B surface antigen containing the preS2 9 amino acid sequence produced by a recombinant yeast.

The hepatitis B virus surface antigen containing the preS2 nine amino acid sequence produced by a recombinant Saccharomyces cerevisiae (yHBsAg) was purified and its physicochemical properties were determined. Ultrastructurally, the yHBsAg was found to be a homogeneous spherical particle with a diameter of 24 +/- 4 nm. The homogeneity of the yHBsAg particles was also demonstrated by analyses of their buoyant density and isoelectric point. They consisted of protein (53%), lipid (36%) and carbohydrate (11%), and the alpha-helix content was estimated to be 32%, differing from the reported values for human plasma-derived HBsAg (hHBsAg). Immunodiffusion analysis showed that the antigenic specificity of yHBsAg was identical to that of hHBsAg. Immunization of mice demonstrated that the immunogenicity of the yHBsAg was significantly higher than that of hHBsAg. </p

The BRST Operator for the Large N=4N=4 Superconformal Algebra

We review the detailed structure of the large $N=4$ superconformal algebra, and construct its BRST operator which constitutes the main object for analyzing $N=4$ strings. We then derive the general condition for the nilpotency of the BRST operator and show that there exists a line of critical $N=4$ string theories.Comment: Latex file, 16 pages, NBI-HE-94-1