A Global Perspective on the Population Structure and Reproductive System of Phyllosticta citricarpa.

The citrus pathogen Phyllosticta citricarpa was first described 117 years ago in Australia; subsequently, from the summer rainfall citrus-growing regions in China, Africa, and South America; and, recently, the United States. Limited information is available on the pathogen's population structure, mode of reproduction, and introduction pathways, which were investigated by genotyping 383 isolates representing 12 populations from South Africa, the United States, Australia, China, and Brazil. Populations were genotyped using seven published and eight newly developed polymorphic simple-sequence repeat markers. The Chinese and Australian populations had the highest genetic diversities, whereas populations from Brazil, the United States, and South Africa exhibited characteristics of founder populations. The U.S. population was clonal. Based on principal coordinate and minimum spanning network analyses, the Chinese populations were distinct from the other populations. Population differentiation and clustering analyses revealed high connectivity and possibly linked introduction pathways between South Africa, Australia, and Brazil. With the exception of the clonal U.S. populations that only contained one mating type, all the other populations contained both mating types in a ratio that did not deviate significantly from 1:1. Although most populations exhibited sexual reproduction, linkage disequilibrium analyses indicated that asexual reproduction is important in the pathogen's life cycle.

Cytogenetics at the University of Cape Town: A 45-year journey.

This article is a brief record of the cytogenetics laboratory from its birth in 1971, under the auspices of the University of Cape Town, throughout its development within the Department of Human Genetics, under the leadership of Professor Peter Beighton, to its present position at Groote Schuur Hospital, as a multidisciplinary unit run by the National Health Laboratory Service.

Predicted v. real prevalence of the 22q11.2 deletion syndrome in children with congenital heart disease presenting to Red Cross War Memorial Children's Hospital, South Africa: A prospective study.

BACKGROUND: The 22q11.2 deletion syndrome (22qDS) has more than 180 associated phenotypic features, yet genotype-phenotype correlation remains obscure. Since many of the clinical characteristics are serious, yet treatable (including congenital heart disease), clinicians must maintain a high index of clinical suspicion to recognise a suite of co-occurring phenotypic features that suggest a diagnosis of 22qDS. Óskarsdottir's scoring schedule (the 'O score') is generally used to suggest the need for confirmatory fluorescent in situ hybridisation (FISH) testing, using the TUPLE 1 probe. An O score of two or more indicates the need for FISH testing. Objectives. A previous audit of FISH-positive results of patients with congenital heart disease at Red Cross War Memorial Children's Hospital (RCWMCH) revealed a clinical recognition rate of 1.7%. However, we were concerned that the syndrome may be under-recognised in our setting. Our aims were therefore to assess the predictive value of 'O scoring' and to accurately determine the prevalence of 22qDS in our patient population. Methods. A prospective trial of FISH testing every new patient with congenital heart disease presenting to RCWMCH was undertaken to accurately determine the prevalence of 22qDS. The results were then compared with the ability of the O score to indicate the need for FISH testing. RESULTS: Testing of 125 patients detected deletions in six (4.8%, 2.8 times the previously determined clinical detection rate), thereby vindicating our concern that 22qDS is under-diagnosed. Of these 125 patients, 37 had an O score of 2 or 3, yet only 6 were FISH-positive, giving the O score a positive predictive value of only 14%. Conclusion. Until a more robust alternative recognition tool is available, South African clinicians should use all clinical recognition criteria liberally to suggest the need for formal testing for 22qDS.

Application of Azoxystrobin for Control of Benomyl-Resistant Guignardia citricarpa on 'Valencia' Oranges in South Africa.

Azoxystrobin was evaluated in replicated small-plot trials from 1995 to 1999 for control of citrus black spot (CBS) on 'Valencia' oranges caused by Guignardia citricarpa. Applications of different rates of tank mixes of azoxystrobin and mancozeb during the susceptible period from October to January were compared with an untreated control as well as the standard four applications of mancozeb with or without mineral oil (1.20 g a.i./liter + 0.5% [vol/vol]/liter and 1.60 g a.i./liter of water, respectively). Two applications of azoxystrobin in tank mixtures with mancozeb and mineral oil (0.5% [vol/vol]/liter) in mid-November and mid-January at rates of 0.10, 0.15, and 0.20 g a.i./liter controlled CBS by more than 98 to 99%, 99 to 100% and 95 to 98%, respectively. Concomitantly, where mineral oil was not added to the fungicide mixture, azoxystrobin and mancozeb resulted only in 73 to 95%, 74 to 93% and 92.2 to 92.3% CBS control, respectively. Tank mixtures of benomyl, mancozeb, and mineral oil reduced CBS by only 29%, which could be attributed to the presence of benomyl-resistant pathogen isolates in the experimental orchard. Azoxystrobin applied at rates of 0.05, 0.075, and 0.10 g a.i./liter in tank mixtures with mancozeb (1.2 g a.i./liter) and mineral oil (0.5% [vol/vol]/liter of water) or Agral 90 (0.5% [vol/vol]/liter of water) were equally effective, reducing CBS by more than 99%. When mineral oil was compared to different adjuvants in tank mixtures with azoxystrobin and mancozeb, only mineral oil resulted in 100% clean exportable fruit. There was no difference between Sunspray 6E and Bac oil when mixed with azoxystrobin and mancozeb on the degree of disease control. Furthermore, the concentration of mineral oil in water can be lowered from 0.5% (vol/vol)/liter of water to 0.3% (vol/vol)/liter of water without a loss in efficacy against CBS. It is therefore, recommended that azoxystrobin (0.075 g a.i./liter) must be applied in tank mixtures with mancozeb (1.2 g a.i./liter) and mineral oil, which can be applied at either 0.5% (vol/vol)/liter of water or 0.3% (vol/vol)/liter of water.

[What influence do size and placement of patella resurfacing have on knee endoprosthesis?]. / Welchen Einfluss hat die Grösse und Platzierung des Patellarückflächenersatzes bei Knieendoprothesen?

The aim of this study was to document the changes in retropatellar pressure, contact area and forces due to different sizes and placement of the patella resurfacing in knee arthroplasty. Six cadaver specimens (after Thiel fixation) were examined after the implantation of the total knee arthroplasty Genesis I. The patella sizes "small" and "medium" were placed as the "onlay" version, centered as well as off-centered by 0.4 cm in all four directions. Pressure and area measurements were done with Fuji pressure measuring film, which was placed between the patellar fascia of the femur and the patella in a defined position. The pressure was measured by applying a predetermined force for 5 s. The examinations were done with 60 degrees knee flexion and a force of 280 N. In our results there were no significant differences between, patella sizes. No significant differences for the medial, distal and proximal placement were found for the small patella. The lateral placement led to a significant decrease in the contact area (P = 0.0277), maximum pressure (P = 0.0422) and force (P = 0.0277). The average pressure did not change significantly (P = 0.1159). For the medium size patella there were no significant differences for medial or distal placement. The comparison of lateral and central placement revealed a significant decrease in the contact area (P = 0.0446). Comparing distal and proximal positioning, a significant increase in contact area and significant decrease in force were found (P = 0.0277 and P = 0.0277 respectively). In conclusion, the choice of small or medium patella resurfacing does not seem to have a significant influence. In comparison to the results without patella implants, the implantation of the small patella caused a significant decrease in the retropatellar contact area (P = 0.03) and force (P = 0.03). Average and maximum pressure did not change significantly (P = 0.6 and P = 0.35) even though pressure increased slightly. For the medium size, maximum pressure (P = 0.03) increased significantly and force decreased significantly (P = 0.0277) whereas contact area and average pressure increased slightly. The results of the different placements of the patella implant do not support the recommendation for a medial shift. However, at least the lateralized implantation led to a reduction of contact area and force as well as to a slight increase of pressure which is considered as unfavorable.

Nonpathogenic Isolates of the Citrus Black Spot Fungus, Guignardia citricarpa, Identified as a Cosmopolitan Endophyte of Woody Plants, G. mangiferae (Phyllosticta capitalensis).

ABSTRACT The population structure of Guignardia citricarpa sensu lato (anamorph: Phyllosticta citricarpa), a fungus of which strains pathogenic to citrus are subject to phytosanitary legislation in the European Union and the United States, was investigated. Internal transcribed spacer sequences revealed two phylogenetically distinct groups in G. citricarpa. This distinction was supported by amplified fragment length polymorphism analysis that also supported the exclusion of two isolates that had apparently been misclassified as G. citricarpa. On cherry decoction agar, but not on other media, growth rates of group I isolates were lower than those of group II isolates. Conidial dimensions were similar, but group I isolates formed conidia with barely visible mucoid sheaths, whereas those of group II formed conidia with thick sheaths. Cultures of isolates belonging to group I produced rare infertile perithecia, whereas fertile perithecia were formed by most isolates of group II. Colonies of isolates belonging to group I were less dark than those of group II, with a wider translucent outer zone and a lobate rather than entire margin. On oatmeal agar, exclusively group I isolates formed a yellow pigment. Group I harbored strains from citrus fruits with classical black spot lesions (1 to 10 mm in diameter) usually containing pycnidia. Group II harbored endophytic strains from a wide range of host species, as well as strains from symptomless citrus fruits or fruits with minute spots (<2-mm diameter) without pycnidia. These observations support the historic distinction between slowly growing pathogenic isolates and morphologically similar fast-growing, nonpathogenic isolates of G. citricarpa. The latter proved to belong to G. mangiferae (P. capitalensis), a ubiquitous endophyte of woody plants with numerous probable synonyms including G. endophyllicola, G. psidii, P. anacardiacearum, and P. theacearum. G. mangiferae occurs in the European Union and the United States on many host species including citrus, and does not cause symptoms of citrus black spot, justifying its exclusion from quarantine measures.

Retropatellar contact characteristics in total knee arthroplasty with and without patellar resurfacing.

Total knee replacement with and without patellar resurfacing was performed in 6 cadaver specimens. The contact pressure and contact area between femur and patella was measured at 60 degrees of flexion. In comparison to specimens without resurfacing the specimens with small size resurfacing showed a significant decrease in contact area, whereas average and maximum pressure were unchanged. In specimens with medium size resurfacing, contact area and average pressure increased slightly, whereas maximum pressure increased significantly. Patellar resurfacing did not change the retropatellar pressure, but was associated with reduced contact area.

[What retropatellar changes result by implantation of a superficial knee joint prosthesis?]. / Welche retropatellaren Veränderungen entstehen durch die Implantation einer Oberflächenkniegelenkprothese?

The aim of this study was to evaluate the retropatellar pressure, force, and contact area in cases of knee arthroplasty compared to knees without arthroplasty. We examined six leg specimens before and after knee arthroplasty. The modified Thiel fixation was used, and arthroplasty was the Genesis I without patellar implant (Fa. Smith & Nephew, Schenefeld). Contact measurements were performed with pressure-sensitive film (Fuji Prescale type "super low") in 45 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion. The results were evaluated with special software, "Pressure Imaging and Analyzing System FPD-901 Series". The leg was exarticulated in the hip joint and the knee joint was opened from a suprapatellar approach. The film was placed at a defined area between the facies patellaris of the femur and facies articularis of the patella. Instantaneous pressure was measured during a time of 5-s pressure increase and a further 5 s. A force of 280 N was applied to the quadriceps muscle. Before knee arthroplasty, the contact area measured 154.3 mm2, the average pressure was 1.14 MPa, the force 182.13 N. After knee arthroplasty, the contact area was 119.94 mm2, the average pressure 1.522 MPa, the force 180.98 N. Following knee arthroplasty the contact area decreased significantly (P = 0.015), and the average (P = 0.0001) and maximum pressure (P = 0.0003) increased significantly. The force did not change significantly (P = 0.7642). The choice of the knee arthroplasty implant and approach to the knee joint should be considered in order to achieve an increased retropatellar contact area thus preventing smaller contact areas than before knee arthroplasty. The increased contact area could also prevent increasing retropatellar pressures after knee arthroplasty and further complications.

[Effect of knee joint flexion and femur rotation on retropatellar contact of the human knee joint]. / Der Einfluss von Kniegelenkbeugung und Femurrotation auf den retropatellaren Kontakt des menschlichen Kniegelenkes.

The aim of the present study was to evaluate retropatellar contact characteristics at different angles of flexion of the knee joint. To this end, 6 cadaveric legs were examined using pressure sensitive film (Fuji Prescale type "super low") at angles of flexion of 45 degrees, 60 degrees, 90 degrees and 120 degrees both in neutral rotation and 10 degrees internal and external rotation of the femur in the same knee joints. A force of 140 N was applied to both the vastus medialis and lateralis, and a comparison made with a medially and a laterally dominating muscle force. The contact areas decreased with increasing angles of flexion. The medially dominating muscle traction increased the contact area. Comparison between internal and external rotation revealed a decrease in contact area on internal rotation. The pressure measurements were comparable in all loading situations. Comparison between neutral and medial traction revealed significant differences in contact area, pressure and force. The influence of femoral rotation showed no significant difference. A comparison of the different angles of flexion revealed only few significant differences. To prevent the development of retropatellar arthrosis, maximum contact areas are necessary. The study has shown an advantage for medially dominating muscle traction, and external rotation of the femur.

Rind Stippling on Valencia Oranges by Copper Fungicides Used for Control of Citrus Black Spot in South Africa.

Four copper sprays and copper mixtures with dithiocarbamates aggravated stippling of the fruit rind of Valencia oranges if sprayed in succession at registered rates during the recommended protection period from October to January for control of citrus black spot in South Africa. Copper stippling was more severe on treatments in which copper oxychloride was sprayed in succession, individually, or in combination with mancozeb or maneb/ZnO. On the other hand, less copper stippling was observed on treatments in which three mancozeb applications were altered with a single copper oxychloride as tank mixtures with or without mancozeb, which was sprayed during midsummer (December and January). Cupric hydroxide resulted in more general copper stippling lesions than any other copper oxychloride spray program. Four successive applications of the wettable powder copper oxychloride formulation resulted in more copper stippling when compared with the suspension concentrate formulation. Stippling was calculated to be more severe with late applications of copper fungicides during December and January. In another experiment, all contact fungicides tested were effective in controlling citrus black spot.

Effects of isoprenaline and glucagon on insulin secretion from pancreatic islets.

The effects of isoprenaline and glucagon on insulin secretion from pancreatic islets were investigated. In the presence of high concentrations of isoprenaline (10-50 mumol/l), glucose-induced (20 mmol/l) insulin secretion from isolated perifused mouse islets was inhibited. This inhibition was apparently mediated by alpha 2-adrenoceptors, as it was antagonized by rauwolscine. At low concentrations isoprenaline (0.1 or 1 mumol/l) did not affect glucose-induced (2.5; 10 or 20 mmol/l) insulin secretion from perifused mouse or rat islets, even if alpha 2-adrenoceptors were blocked by rauwolscine. A stimulatory effect of isoprenaline on insulin secretion was also not observed in the perfused rat pancreas. However, when incubated mouse islets were exposed to glucose (10 mmol/l), insulin secretion was further enhanced by isoprenaline (0.5 mumol/l). To elucidate the underlying mechanism, the effects of glucagon on insulin secretion were investigated, because glucagon is released from the pancreatic A-cells during stimulation with isoprenaline and is accumulated in the islets and the surrounding medium during incubations of pancreatic islets. Indeed, glucagon stimulated insulin secretion from perifused mouse islets in the presence of high glucose (10 or 15 mmol/l) concentrations but not of low glucose (5 mmol/l) concentrations. Thus it is concluded that direct beta-adrenergic stimulation of pancreatic B-cells does not occur in mouse or rat pancreatic islets. Augmentation of glucose-induced insulin secretion by isoprenaline observed in incubation systems can be explained as a result of stimulation by glucagon, which is released from pancreatic A-cells by isoprenaline.