The evolutionary history of chromosomal super-integrons provides an ancestry for multiresistant integrons.

Integrons are genetic elements that acquire and exchange exogenous DNA, known as gene cassettes, by a site-specific recombination mechanism. Characterized gene cassettes consist of a target recombination sequence (attC site) usually associated with a single open reading frame coding for an antibiotic resistance determinant. The affiliation of multiresistant integrons (MRIs), which contain various combinations of antibiotic resistance gene cassettes, with transferable elements underlies the rapid evolution of multidrug resistance among diverse Gram-negative bacteria. Yet the origin of MRIs remains unknown. Recently, a chromosomal super-integron (SI) harboring hundreds of cassettes was identified in the Vibrio cholerae genome. Here, we demonstrate that the activity of its associated integrase is identical to that of the MRI integrase, IntI1. We have also identified equivalent integron superstructures in nine distinct genera throughout the gamma-proteobacterial radiation. Phylogenetic analysis revealed that the evolutionary history of the system paralleled that of the radiation, indicating that integrons are ancient structures. The attC sites of the 63 antibiotic-resistance gene cassettes identified thus far in MRIs are highly variable. Strikingly, one-fifth of these were virtually identical to the highly related yet species-specific attC sites of the SIs described here. Furthermore, antimicrobial resistance homologues were identified among the thousands of genes entrapped by these SIs. Because the gene cassettes of SIs are substrates for MRIs, these data identify SIs as the source of contemporary MRIs and their cassettes. However, our demonstration of the metabolic functions, beyond antibiotic resistance and virulence, of three distinct SI gene cassettes indicates that integrons function as a general gene-capture system for bacterial innovation.

[Metabolic recovery of rat muscle after reparative microsurgery of peripheral nerves as a function of suture technics]. / Récupération métabolique du muscle de rat après microchirurgie réparatrice du nerf périphérique en fonction des techniques de suture.

In the rat, a characteristic response to motor denervation is an increased flow of inorganic phosphate across the muscle cell membranes. This reaction is specific for the neurogenic atrophy and is fully reversible on reinnervation. In the present study, the muscle cell permeability to inorganic phosphate has been used as a criterion in assessing the efficiency of four different techinques. Microsurgery was carried out on peroneal nerve using a Zeiss OMP I operating room microscope. The technique were: I. Bringing together the two nerve segments with two epineural stitches (Ethilon 11/0 thread). II. Tight suture with eight epineural stitches (Ethilon 11/0 thread). III. As in II but with SSC 11/0 thread. IV. As in III but combined with postoperative corticotherapy. 32P radiophosphate incorporation was measured in the extensor digitorum longus and in the tibialis anterior. The best results were obtained with the first and simpler procedure. However, in some respects, equivalent results were observed with the fourth procedure associating a tight suture with postoperative corticotherapy. It follows that in the rat, it is indicated either to minimize the surgical trauma or to counteract the fibrosis attending the surgical trauma.

[Experimental models of vascular microsurgery on small-calibre arteries]. / Modèles expérimentaux de microchirurgie vasculaire sur les artères de petit calibre.

The authors, after studying the various types of microvascular sutures performed by participants at the Microsurgical Course (Dr Ph. Ploncard) from the Brussel University during a chosen period of over one year, draw several conclusions concerning the results in order to explain the main failures that may be found--aneurysms, stenosis, thrombosis--after surgery. The indications of this type of training are pointed out-extra-intracranial by pass, coronary by pass, flap revascularisation, etc... A good technique gained after an intense training together with an obvious individual predisposition are according to the authors the two main reasons of success in this meticulous surgery.

[The surgery of peripheral nerves. New perspectives in treatment by the microsurgical techniques (author's transl)]. / La chirurgie des nerfs périphériques. Nouvelles perspectives de traitement par les techniques micro-chirurgicales.

The author describes the different techniques of reconstructive surgery of peripheral nerves and the failures that marked these trials until the advent of microsurgical techniques. After stressing the importance of the biology and physiopathology of a traumatized nerve and its stem cells, the author detailes the regeneration stages of the nerve cell when ideal conditions of axonal alignment are established by microtechniques. Considering the different notions of biology and pathology in relation to the time delay between the traumatism and referral to the surgeon, the author insists on the absolute necessity of operating during the period of full regeneration of the nerve cell, i.e. within the first 6 months.

[Experimental comparative study of microsurgical nerve sutures. II. Water-proof sutures and suture by simple approximation of the stumps]. / Etude comparative expérimentale de sutures nerveuses microchirurgicales. II. Les sutures imperméables et les sutures par simple rapprochement des tronçons.

After having demonstrated in a previous paper the advantages of an early surgical repair of injured nerves over a delayed suture, the author, following the same methods--electrophysiological and histological controls--comes to the conclusion that the so-called water-proof suture technique compared with a simple bringing up together of both stumps of the nerve, gives by far higher degrees of regeneration.

[Comparative experimental study of microsurgical nerve suture. I. Immediate suture and delayed suture]. / Etude comparative expérimentale de suture nerveuse microchirurgicale. I - Suture immédiate et suture retardée

Impressed by multiplicity of theories and conceptions concerning nerve surgery and by the difficulty to draw grouded conclusions from the different and contradictory work available from the litterature on the subject, the author makes a revision of the biology of the nerve, to be used as a point of departure for investigation. Based on the fact that protheosynthesis capacity of the nerve cell is known to be at its top value during the first week after the lesion of the nerve, the author endeavours to compare immediate suture with delayed suture. This comparative study is based both on electrophysiological and histological data and show clearly enough the real advantage of trying nerve reconstruction as early as possible, to avoid progression of devitalisation and invasion by fibrosis of both stumps. The surgical procedures are made with the help of the operating microscope and the same technique is used in both groups.

Comparative study of circumferential nerve suture using the operating microscope. Electrophysiological and histological control.

The aim of this work is to try to compare the results of different methods of circumferential small nerve suture according to the degree of magnification and type of microsurgical technique. Four techniques were studied in forty Wistar rats. 1. Microsurgical suture with the Set technique. Magnification 25, accurate suture. 2. Microsurgical suture with simple end to end approximation. Magnification 25, accurate suture. 3. Same technique, but delayed suture. 4. Suture with a simple end to end approximation. Magnification 4. Four stitches for reapproximation. After four months the sutured nerves have been studied both electrophysiologically and histologically. The results show clearly that the so-called set technique associated with an accurate circumferential suture with eight stitches under high magnification gives by far the best results, the regeneration rate of the nerve being higher than 80%. The results in groups 3 and 4 are definitely less good. The simple bringing together of both stumps under low magnification with only four stitches (group 4) gives the worst results with only 20% of regeneration.