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INTRODUCTION: Laparoscopy for small bowel obstruction (SBO) has increasingly been performed for the advantages minimally invasive surgery provides. However, its benefit remains unclear. METHODS: From January 2004 to July 2011, we enrolled 28 consecutive patients who underwent a laparoscopic operation for SBO, secondary to postoperative adhesions. We compared the results of SBO patients treated laparoscopically with those of 25 patients who underwent conventional open laparotomy in a retrospective matched-pair analysis. RESULTS: Laparoscopic treatment was completed in 25 patients (89%), including 17 laparoscopic-assisted cases. The mean procedural time was 112 minutes in the laparoscopic group and 79 minutes in the open group (P < 0.05). Patients resumed oral intake after a mean of 3 days in the laparoscopic group compared with a mean of 6.5 days in the open group (P < 0.05). The length of hospital stay was 11 and 22 days (P < 0.05), respectively, in the laparoscopic and open groups. Postoperative complications occurred in two patients in the laparoscopy group and 14 patients in the open group (P < 0.05). CONCLUSION: The laparoscopic approach was effective for the management of mechanical SBO in selected patients. Furthermore, minimally invasive laparoscopic adhesiolysis is also feasible and brings the benefit of cosmetic results.

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The unfolding pathway of lysozyme was investigated by carrying out the computer simulation. Taking into account the simultaneous change of both the dihedral angels phi and psi of a residue, we explore the detailed features of the conformational energy profiles. The triangle distance map shows that the lysozyme molecule is divided into three domains, 1-40, 41-101 and 102-129 in amino acid residue numbers (referred to as the domains I, II and III, respectively). The calculated unfolding process indicates that in the early stage of unfolding domain III located at the C-terminal begins to be detached from the other two, and then domain I can be unfolded. The long-range interactions between domains I and III stabilize the whole molecule and give the cooperative nature of the folding. The calculated unfolding pathway of lysozyme is consistent with the folding pathway proposed by Anderson & Wetlaufer [J. Biol. Chem. (1976). 251, 3147-3153] who identified the disulfide bondings in the early stage of the glutathione regeneration. A simplified treatment of unfolding for myoglobin is also discussed in the Appendix.

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Local and small-amplitude conformational fluctuations in hen egg white lysozyme around its native conformation were studied by the Monte Carlo simulation with conformational energy calculation. In order to carry out such a simulation in a shorter computation time, the following method was devised: at each step of the simulation a segment of consecutive four residues, say, i to i + 3, is chosen at random from N residues and then the small conformational change of the segment is performed so that the conformations of the two blocks of residues 1 to i - 1 and i + 4 to N as well as the mutual location of the two blocks are not changed. In this simulation it was found that calculated atomic displacements and fluctuations of dihedral angles well reflect the characteristics of local conformations, for example, stiffness of regular secondary structures and flexibility of non-regular structures, especially of the regions around the lips of the active-site cleft and of the region that undergoes conformational change on ligand binding to the active site. The flexibility of these regions is probably necessary for the reaction of the active site to the ligand. A close correlation between the solvent accessibility of the side chain of each residue and its flexibility was also observed. Furthermore, it was shown that the results obtained in this study are in a good agreement with the same properties observed in analyzing temperature factors derived from refinement of X-ray data of the protein.

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The present paper is devoted to the study of the conformational transition of polypeptides which are capable of forming alpha-helix, beta-structure and random coil conformations with the finite homogeneous chain model. The experimental results on the surfactant-induced conformational change of poly(L-lysine) can be well described by the present model assuming cooperative binding of the surfactant ions to the polypeptide side groups.

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The conformational changes of polypeptides which are capable of forming the alpha-helix. beta-structure and random coil (or the unordered) conformations are discussed. The kinetics of this system are studied as the time evolution of the probabilities describing the conformational states of the system. The time behavior of the average numbers of the alpha-helix and the beta-structure reveals the existence of intermediate states which are not found and not stable at equilibrium. These intermediates make the kinetics of this system more complex. Such situations can occur in protein folding and unfolding processes in such a way that a conformation absent in the tertiary structure appears in the intermediate stages and disappears finally, and the time course of the reaction is described by the sum of two or more exponential terms, in other words, the protein folding and unfolding processes display multiphasic kinetics. These intermediates, which are formed by short-range interactions, may usually be destroyed but sometimes can be stabilized by medium- and long-range interactions and remain stable for a fairly long time in the process of renaturation in real proteins.

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