General and specific combining abilities in a maize (Zea mays L.) test-cross hybrid panel: relative importance of population structure and genetic divergence between parents.

KEY MESSAGE: General and specific combining abilities of maize hybrids between 288 inbred lines and three tester lines were highly related to population structure and genetic distance inferred from SNP data. Many studies have attempted to provide reliable and quick methods to identify promising parental lines and combinations in hybrid breeding programs. Since the 1950s, maize germplasm has been organized into heterotic groups to facilitate the exploitation of heterosis. Molecular markers have proven efficient tools to address the organization of genetic diversity and the relationship between lines or populations. The aim of the present work was to investigate to what extent marker-based evaluations of population structure and genetic distance may account for general (GCA) and specific (SCA) combining ability components in a population composed of 800 inter and intra-heterotic group hybrids obtained by crossing 288 inbred lines and three testers. Our results illustrate a strong effect of groups identified by population structure analysis on both GCA and SCA components. Including genetic distance between parental lines of hybrids in the model leads to a significant decrease of SCA variance component and an increase in GCA variance component for all the traits. The latter suggests that this approach can be efficient to better estimate the potential combining ability of inbred lines when crossed with unrelated lines, and limits the consequences of tester choice. Significant residual GCA and SCA variance components of models taking into account structure and/or genetic distance highlight the variation available for breeding programs within structure groups.

The genetic basis of heterosis: multiparental quantitative trait loci mapping reveals contrasted levels of apparent overdominance among traits of agronomical interest in maize (Zea mays L.).

Understanding the genetic bases underlying heterosis is a major issue in maize (Zea mays L.). We extended the North Carolina design III (NCIII) by using three populations of recombinant inbred lines derived from three parental lines belonging to different heterotic pools, crossed with each parental line to obtain nine families of hybrids. A total of 1253 hybrids were evaluated for grain moisture, silking date, plant height, and grain yield. Quantitative trait loci (QTL) mapping was carried out on the six families obtained from crosses to parental lines following the "classical" NCIII method and with a multiparental connected model on the global design, adding the three families obtained from crosses to the nonparental line. Results of the QTL detection highlighted that most of the QTL detected for grain yield displayed apparent overdominance effects and limited differences between heterozygous genotypes, whereas for grain moisture predominance of additive effects was observed. For plant height and silking date results were intermediate. Except for grain yield, most of the QTL identified showed significant additive-by-additive epistatic interactions. High correlation observed between heterosis and the heterozygosity of hybrids at markers confirms the complex genetic basis and the role of dominance in heterosis. An important proportion of QTL detected were located close to the centromeres. We hypothesized that the lower recombination in these regions favors the detection of (i) linked QTL in repulsion phase, leading to apparent overdominance for heterotic traits and (ii) linked QTL in coupling phase, reinforcing apparent additive effects of linked QTL for the other traits.

New insights into the regulation of phytochelatin biosynthesis in A. thaliana cells from metabolite profiling analyses.

In higher plants and some fungi, heavy metals induce the synthesis of chelating peptides known as phytochelatins (PCs). They are characterized by the general structure (gamma-Glu-Cys)n-Gly, but in some plant species, the C-terminal glycine can be replaced by serine, glutamine, glutamate or alanine, leading to iso-phytochelatins (iso-PCs). Although the distribution of iso-PCs is considered to differ from one species to another, we previously showed that Arabidopsis thaliana (A. thaliana) cells are able to synthesize most PC-related peptides (PCs and iso-PCs) described in the literature. We also observed an accumulation of the dipeptide gamma-glutamylcysteine (gamma-EC) when cadmium (Cd) (200 microM) was added to the culture medium, suggesting that either glutathione synthetase or glycine availability could be a limiting factor for the biosynthesis of PC-related peptides. In this context, the aim of the present work was to seek new insights into the regulation of PC synthesis by performing metabolic profiling using liquid chromatography-mass spectrometry. The levels of PC-related peptides and their precursors were measured in A. thaliana cells following Cd exposure. A range of doses (0, 50, 200 and 400 microM CdNO3) and kinetic studies (from 1 to 48 h) showed a dose threshold (50 microM CdNO3) and a lag time between the appearance of PCs and iso-PCs concomitant with the gamma-EC accumulation induced by Cd, occurring at cadmium concentrations above 50 microM. This accumulation was suppressed by supplementation of the culture medium with 25 mM glycine. Glycine supplementation had a limited impact on the concentrations of glutathione and PCs whereas the levels of most iso-PCs were significantly increased. Taken together, these results indicate that GSH is involved in the biosynthesis of the iso-PCs in vivo, and that the biosynthesis of PC-related peptides is limited by the availability of glycine in the presence of high cadmium concentrations.

Optimisation of enzyme concentrations for unbranched reaction chains: the concept of combined response coefficient.

In the metabolic control theory, the control coefficient is a key parameter in quantifying the sensitivity of the flux towards an infinitesimal variation of enzyme activity. This concept does not apply just as it is for variations of enzyme concentrations whenever there is spatial, energy or resources limitations in the cell. Due to constraint on total enzyme concentration, the variation of concentration of any given enzyme may affect the concentrations of other enzymes. To take into account these correlations between enzyme concentrations, we propose the concept of "combined response coefficient". Its definition is similar to that of the control coefficient, but its mathematical expression is different. Its range of variation is from -infinity to +1, the null value corresponding to optimum enzyme concentration, i.e. to concentrations that maximise the flux, and the negative values to concentrations beyond the optimum value. A summation property could be derived using a simple weighting of the combined response coefficients, the sum of the weighed coefficient being 0.

Open wound drainage versus wound excision in treating the modern assault rifle wound.

Military dogma of the past 20 years preaches that excision of all injured tissue around the path of a penetrating projectile is essential in wound treatment. To find out whether excising injured muscle surrounding a bullet path benefits healing over and above the benefit provided by a simple release of tension by incision, two groups of 90 kg swine were shot in the hind leg with a replica of the AK-74 assault rifle projectile. One group was treated by excision of injured tissue around the projectile path; in the other group no tissue was excised. Both groups were given parenteral penicillin for 5 days, and simple gauze dressings were used to cover the wounds. No difference in healing time occurred; the wounds in both groups had closed, and no epithelial defect remained by 20 to 22 days. These results indicate that the simple extremity wound caused by the modern-generation assault rifle, provided with adequate open drainage and systemic penicillin, heals as rapidly when the body defense mechanisms handle the disrupted tissue as when an attempt is made to excise it surgically.

[The role of surgery in acute epididymitis]. / Place de la chirurgie dans les épididymites aiguës.

One third of the acute épididymitis (A.E.) admitted in the Military Hospital in Marseilles have been operated, i.e. 33 cases; out of them the last 12 cases have been systematically monitored by ultrasonography. Twice out of three times, clinical picture suggested a possible twisting that led to an emergency surgical exploration. Interest of ultrasonography of the scrotum is underlined as far as diagnosis is concerned but also in monitoring A.E. Indeed, despite medical treatment (antibiotics + anti-inflammatory drugs), it is possible that some A.E. are evolving either to abscess or to their "vascular" form; The ultimate form of the acute epididymo-orchitis is necrosis of the testis. This is due to, or amplified by, vascular compression linked up with edema. Surgical intervention has therefore to investigate by inguinal path the entire spermatic cord and the épididymis-testis system, and to apply the "decompression technique" requested.

[Ureteral war injuries. Apropos of 3 African cases]. / Les plaies urétérales de guerre. A propos de trois observations africaines.

The war ureteral gunshot wounds (W.U.G.W.) are, in practice, scarce but not an exception. They are to be suspected in every war abdominal injury. Urethral catheterization, microscopic hematuria research, simple X-Ray and I.V.P. have to be undertaken; but it's never easy in wartime circumstances. Investigation must be carried out during intervention: ureteral exploration in case of retroperitoneal hematoma or wound. Three observations illustrate these main difficulties. Unfortunately diagnosis is often done in post-operative time when a complication arises. The treatment is now well known: adequate debridement, anastomosis or reimplantation and drainage.

[Urethral stricture in Africa. Urologic complication of sexually transmitted diseases in the male in Africa]. / Le rétrécissement uréthral en Afrique. Complication urologique des maladies sexuellement transmissibles chez l'homme en Afrique.

Urethral stricture is a very frequent and severe complication of sexually transmitted diseases in African male. It is very often largely sclerous and inflammatory as the patients come to consultation very late. Urethral repair techniques are analysed, so the principles of surgical procedure. When urethral stricture is brief and "catheterisable", and in case of recurrence, endoscopic dilatation or endoscopic internal urethrotomy must be performed in the first place. In the others cases, in order, we advise: free skin graft urethroplasty (Devine), pedicled vaginal urethroplasty (Kishev), scrotal flap urethroplasty (Blandy), and the two-stage urethroplasty. In fact this choice depends on the urethral and peri-urethral lesions and on the operator's practice.

[A case of ureteral bilharziasis followed for 22 years]. / A propos d'une bilharziose uretérale suivie pendant 22 ans.

The authors report on one case of urinary schistosomiasis monitored for 22 years. It illustrated the problems posed by the "bilharzial uretero-hydronephrosis". They analyse the different therapy problems which have to have been successively solved: Low double ureteral stenosis. The difficulty to be certain of such a stenosis is recalled. The possibility of a reflux or an ureteral atony must be eliminated. True stenosis must be operated without delay; Kidney cancer revealed 20 years later through chronic renal failure by vesico-ureteric reflux caused by the first surgical intervention (latero-lateral vesico-ureteric anastomosis); Iatrogenic vesico-ureteral reflux, treated by uretero-vesical implantation on "psoic" bladder with anti-reflux submucous path. The future of such a chronic renal failure is linked to the capability of the remaining ureter to ensure an acceptable passage of urine, and to the rehabilitation possibility of the kidney. Finally, the authors recalled the difficult therapeutic indications in case of ureteral attack due to bilharziosis.

[Genitourinary bilharzioma. Isolated cases of vesical bilharzioma and epididymal bilharzioma]. / Le bilharziome génito-urinaire. Un cas de bilharziome vesical et un cas de bilharziome épididymaire isolés.

The authors report on two isolated cases of bilharzioma: one vesical revealed by an hematuria and one epididymal constituting an intrascrotal mass. Clinical signs did not oriented toward these diagnosis and biology was helpless. Serodiagnosis by hemagglutination was negative, but immunofluorescence was more reliable. On the contrary both tumors were detected by echotomography of which the efficiency is determinant for the diagnosis and must be underlined. Only anatomopathology was able to confirm the diagnosis of tumor. As a matter of course, surgical exploration and excision are necessary in these types of tumors with negative biology. In both cases, effects were isolated. In one patient, infestation was old and already treated; in the second one, infestation was probably light. The authors recall also bilharzioma physiopathology. Frequency of vesical bilharzioma is about 20% of genito-urinary schistosomiasis while epididymal bilharzioma reaches only 0.29 to 4.8%. Direct line between bilharzioma and cancer is likely but controversial, schistosomiasis beeing a true irritative agent.