SUMMARYBy combining Zinnia elegans in vitro tracheary element genomics with reverse genetics in Arabidopsis, we have identified a new upstream component of secondary wall formation in xylary and interfascicular fibers. Walls are thin 1 (WAT1), an Arabidopsis thaliana homolog of Medicago truncatula NODULIN 21 (MtN21), encodes a plant-specific, predicted integral membrane protein, and is a member of the plant drug/metabolite exporter (P-DME) family (transporter classification number: TC 2.A.7.3). Although WAT1 is ubiquitously expressed throughout the plant, its expression is preferentially associated with vascular tissues, including developing xylem vessels and fibers. WAT1:GFP fusion protein analysis demonstrated that WAT1 is localized to the tonoplast. Analysis of wat1 mutants revealed two cell wall-related phenotypes in stems: a defect in cell elongation, resulting in a dwarfed habit and little to no secondary cell walls in fibers. Secondary walls of vessel elements were unaffected by the mutation. The secondary wall phenotype was supported by comparative transcriptomic and metabolomic analyses of wat1 and wild-type stems, as many transcripts and metabolites involved in secondary wall formation were reduced in abundance. Unexpectedly, these experiments also revealed a modification in tryptophan (Trp) and auxin metabolism that might contribute to the wat1 phenotype. Together, our data demonstrate an essential role for the WAT1 tonoplast protein in the control of secondary cell wall formation in fibers.

Although, of itself, conversion is not considered to be a complication of laparoscopic surgery, it is true that the postoperative course after conversion is associated with appreciably poorer results in terms of morbidity, mortality, convalescence, blood transfusion requirement, and postoperative hospital stay. The importance of experience in laparoscopic surgery can be demonstrated on the basis of the conversion rates. Careful patient selection oriented to the experience of the surgeon is required if we are to keep the conversion, morbidity, and mortality rates of laparoscopic colorectal procedures as low as possible.

Laparoscopic colorectal surgery is very demanding, and can be performed with low morbidity and mortality rates only by a surgeon with above-average experience with this type of surgery and a large caseload of laparoscopic colorectal procedures. The learning curve for such procedures is appreciably longer than for other laparoscopic operations. With increasing experience, technically more demanding operations, including radical oncologic rectal laparoscopic procedures, can be performed with appreciably reduced operating times and conversion rates, but with no increase in morbidity or mortality.

We investigated the relation between cell wall structure and the resulting mechanical characteristics of different plant tissues. Special attention was paid to the mechanical behaviour beyond the linear-elastic range, the underlying micromechanical processes and the fracture characteristics. The previously proposed model of reorientation and slippage of the cellulose microfibrils in the cell wall [H.-CH. Spatz et al. (1999) J Exp Biol 202:3269-3272) was supported and is here refined, using measurements of the changes in microfibrillar angle during straining. Our model explains the widespread phenomenon of stress-strain curves with two linear portions of different slope and sheds light on the micromechanical processes involved in viscoelasticity and plastic yield. We also analysed the velocity dependence of viscoelasticity under the perspective of the Kelvin model, resolving the measured viscoelasticity into functions of a velocity-dependent and a velocity-independent friction. The influence of lignin on the above-mentioned mechanical properties was examined by chemical lignin extraction from tissues of Aristolochia macrophylla Lam. and by the use of transgenic plants of Arabidopsis thaliana (L.) Heynh. with reduced lignin content. Additionally, the influence of extraction of hemicelluloses on the mechanical properties was investigated as well as a cell wall mutant of Arabidopsis with an altered configuration of the cellulose microfibrils.

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Laparoscopic colorectal interventions in sigmoid diverticulitis are, for the most part, carried out as elective procedures for peridiverticulitis, stenosis, or recurrent attacks of inflammation. The conversion, complication, and mortality rates associated with these interventions are acceptable. Laparoscopic procedures in Hinchey stages I to IV sigmoid diverticulitis and in the presence of fistula and bleeding are more likely to be associated with complications, and should be carried out only by highly experienced laparoscopic surgeons.

In principle, laparoscopic anterior resection with curative intent generates considerably more reservations than laparoscopic abdominoperineal resection, which is technically much easier to perform.

The widely used Mayo procedure leads to unacceptable results for repair of incisional hernias and other techniques should be evaluated and used more often. Repair of an incisional hernia does not improve overall quality of life.