Comparative histochemical analyses of oxidative burst and cell wall reinforcement in compatible and incompatible melon-powdery mildew (Podosphaera fusca) interactions

The spatial-temporal expression patterns of oxidative burst and cell wall reinforcement were analyzed in leaves of resistant and susceptible melon (Cucumis melo L.) cultivars in response to Podosphaera fusca (Fr.) Braun & Shishkoff, the main causal agent of powdery mildew in cucurbits. Extensive development of powdery mildew mycelia and a progressive increase in haustorial count were recorded in the susceptible cultivar after 4d, while in the resistant cultivar powdery mildew failed to grow and small brownish and necrotic leaf areas were frequently observed. Rapid generation of the reactive oxygen intermediates hydrogen peroxide and superoxide radicals 4h after pathogen challenge, but before the fungal haustoria formation, stood upstream in the cascade of events induced during these interactions. This oxidative burst was followed by the accumulation of strengthening polymers of callose and lignin at the cell wall of attacked resistant plant cells. Interestingly, the transcriptional levels of phenylalanine ammonia-lyase (PAL), an important enzyme for phenylpropanoid metabolism, did not significantly change throughout the experiments. Although these physiological changes were observed in both cultivars, their faster kinetics and amplitude in the resistant line compared to the susceptible cultivar governed the differential visual response of these cultivars against P. fusca. These findings, along with data obtained in previous studies, have provided the bases for an integrated model in which the spatial-temporal response patterns of these resistance mechanisms have been arranged, which may ultimately lead to successful protection of melon plants against P. fusca.

Up-regulation and localization of asparagine synthetase in tomato leaves infected by the bacterial pathogen Pseudomonas syringae

Nitrogen metabolism is one aspect of basic metabolism, which is still quite unknown in the field of plant-pathogen interactions. Evidence derived from previous studies conducted in our laboratory strongly suggests that during microbial pathogenesis an important nitrogen mobilization process takes place in diseased tissues. Here we describe the expression pattern of asparagine synthetase (AS; EC 6.3.5.4) in tomato leaves infected by the bacterial pathogen Pseudomonas syringae pv. tomato. Using an homologous AS cDNA probe isolated by RT-PCR from infected leaves, we have observed a high level induction of AS expression during the course of infection. Concomitantly, a single AS polypeptide also accumulated in response to bacterial infection. Furthermore, immunohistochemical analysis of AS in infected leaves revealed a strong immunostaining in phloem cells of the main vascular bundles and in secondary veins of the leaf blade. These data correlate with those previously reported for expression of a cytosolic isoform of glutamine synthetase (GS1) also induced during development of the infectious process. Taken together, our results suggest the existence of a GS1/AS pathway representing a metabolic route for transferring ammonium released from protein catabolism into asparagine, an amino acid that may have a major role in nitrogen mobilization from diseased tissues.

Isolation and evaluation of antagonistic bacteria towards the cucurbit powdery mildew fungus Podosphaera fusca

Powdery mildew is one of the most important limiting factors for cucurbits production in Spain, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibility of exploiting antagonistic bacteria in the biological control of the cucurbit powdery mildew fungus Podosphaera fusca (syn. Sphaerotheca fusca). Among a collection of bacterial strains isolated from distinct cucurbit powdery mildew diseased plants and rhizospheric soils, four isolates were selected, by means of a screening method based on antibiotic production, and identified as Bacillus spp. These isolates proved to be efficacious in the control of cucurbit powdery mildew in in vitro detached leaves and seedling biocontrol assays, where reductions of disease severity of up to 80% were obtained. Furthermore, bacterial populations on melon leaves remained at similar levels (10(5) cfu cm(-2)) over the 16-day period studied and, as observed by scanning electron microscopy analysis, they were able to establish microcolonies associated with an extracellular matrix, which reveals that these isolates efficiently colonize melon phylloplane. These results indicate that the bacterial isolates selected are promising candidates for biological control agents of cucurbit powdery mildew in southern Spain.

Comparison of C0 and C2 cyclosporine monitoring in long-term renal transplant recipients

Recent data show that monitoring cyclosporine A (CsA) concentrations with 2-hour postdose levels (C2) correlates with the incidence of rejection and graft outcome in de novo renal transplant patients. The purpose of the present work was to evaluate the advantage of C2 monitoring after the first year of kidney transplantation. We studied 161 patients, 96 on CsA-prednisone and 65 on triple therapy (Aza or MMF) who had been transplanted for a mean of 103+/-44 months. Mean serum creatinine (SCr) was 1.65+/-0.69 mg/dL, mean C0 was 174+/-44, and C2 was 667+/-194 ng/mL. Patients were classified according to C2 values: >850 (n=29), between 850 and 450 (n=109), and <450 (n=23) ng/mL. Patients with C2 <450 ng/mL displayed higher SCr values (1.97+/-0.99; 1.59+/-0.51; 1.52+/-0.4 mg/dL; P<.001), received lower CsA doses (172+/-54; 207+/-54; 227+/-56 mg/d, P<.01), showed lower C0 levels (155+/-48; 172+/-41; 199+/-45 ng/mL; P< .001), and included more patients on triple therapy (54.5%; 44%; 17.2%; P<.05). We found weak correlations between C0 and C2 (r=0.37), between C2 and CsA dose (r=0.36), and between C0 and SCr (r=-0.37). Among 117 patients followed up for 1 year with several C0 and C2 measurements, the coefficient of variation of C0 was 17% and of C2 was 21%. Graft functional deterioration occurred in 16 patients independent of the differences among the C2 groups, but 7 recipients (43.7%) had C0 <150 ng/mL and C2/C0 >5. We conclude that C2 in monitoring stable patients needs further evaluation.

Renal transplant recipient outcome after losing the first graft

Renal transplantation is the optimal therapy for end-stage renal failure and considerable attention has been given to graft and patient survival and the effectiveness of immunosuppressive regimens. However, little attention has been given to outcome for patients who lose their grafts. We retrospectively reviewed the outcomes of the 793 first renal transplants performed at our institution between November 1979 and December 2001. A total of 348 patients lost their grafts, 116 by death with a functioning graft (33.3%) and 232 patients for other causes (66.7%). Eighty-six patients (37.1%) received a second transplant 3.5+/-2.4 years after returning to dialysis and the remainder continued on dialysis. Retransplanted patients were younger at the time of the first transplant (P=.000), and both time on dialysis (P=.012) and duration of graft function (P=.057) were shorter than for those remaining on dialysis. Therefore, retransplant patient survival at 1, 5, and 10 years was better than among those patients on dialysis not included on the waiting list (P<.001), but when compared with the relisted patients the survival rate was almost identical (96%, 85%, and 67% vs 97%, 82%, and 67%; P=NS). Almost 40% of patients who lost their first grafts were retransplanted. We did not observe differences in patient survival between retransplant and relisted patients. Because the number of cases is limited, our results need to be confirmed by larger series.

Effect of mycoparasitic fungi on the development of Sphaerotheca fusca in melon leaves

We evaluated the possibilities of exploitation of several mycoparasitic fungi in the biocontrol of cucurbit powdery mildew (Sphaerotheca fusca) in melon greenhouses. To simplify the screening, an in vitro biological control test on detached leaves of melon has been used and a detailed microscopic analysis of the interactions between mycoparasites and S. fusca conducted. In this context, the effect of mycoparasitic fungi on the formation of infection structures of S. fusca such as haustoria, conidia and conidiospores has been quantified. On the basis of the microscopic data, effect of mycoparasites on severity and incidence of cucurbit powdery mildew has been discussed. Our results show that, under controlled environmental conditions, Acremonium alternatum, Ampelomyces quisqualis and especially Lecanicillium lecanii, when applied in early stages of infection, were able to significantly reduce cucurbit powdery mildew symptoms and S. fusca development on melon leaves. These results indicate that these mycoparasites are promising candidates for the biocontrol of cucurbit powdery mildew in melon greenhouses.

Outcome of cadaveric renal transplant patients treated for 10 years with cyclosporine: is chronic allograft nephropathy the major cause of late graft loss?

BACKGROUND

The introduction of cyclosporine (CsA) has improved the short-term outcome of renal transplantation, but its effect on the long-term survival is not well known.

METHODS

We analyzed 128 cadaveric first renal transplant recipients with CsA and prednisone as basal immunosuppression followed for at least 10 years, and we have compared them with a group of 185 historical patients treated with azathioprine (Aza) and prednisone.

RESULTS

The 1-year graft survival was 83% in the CsA-treated patients and 68% in the Aza-treated patients (P<0.025), and the differences were significant for 3 years. Acute rejection accounted for the 10.9% of losses in CsA-treated patients and for 23.8% of losses in Aza-treated patients (P=0.046). Chronic allograft nephropathy was the cause of graft losses in 40.6% and 16.8% of cases (P=0.008). Patient survival at 5 years was 88% in CsA-treated patients and 79% in the Aza-treated patients (P<0.025). When analyzing the data of the 64 CsA-treated patients and the 84 Aza-treated patients with one functioning graft at 10 years, mean serum creatinine values were significantly higher in the CsA-treated patients at all time points but the increases were not significantly different. At 10 years, mean blood pressure was higher (P=0.002), and hypercholesterolemia (P=0.011) and hyperuricemia (P=0.000) were more prevalent in the CsA-treated patients.

CONCLUSIONS

CsA resulted in a better short-time patient and graft survival that was not maintained in the long-term outcome. Chronic allograft nephropathy was the leading cause of graft loss in CsA-treated patients. Graft function was poorer in the CsA-treated patients, but its decline was similar in the two groups.

Delayed graft function does not reduce the survival of renal transplant allografts

BACKGROUND

The aim of the present study was to investigate the effect of delayed graft function (DGF) in graft outcome when adjusted by the presence of acute rejection in the first month after transplantation.

METHODS

A total of 437 cadaveric renal transplant patients on cyclosporine and steroids were included in the study. Variables related to donor, recipient, and graft were prospectively collected.

RESULTS

The incidence of DGF was 44.4%. When patients dying with a functioning graft were censored, graft survival rates at 1 and 6 years were similar in patients with immediate function to those with DGF, when rejection was not present (96% and 81% vs. 95% and 83%, respectively). Rejection negatively influenced graft survival rates at 1 and 6 years, both in patients with immediate graft function (80% and 73%, P<0.05 vs. no DGF/no rejection) and more deeply in those with associated DGF (77% and 62%, P<0.001 vs. no DGF/no rejection). Rejection was more frequently diagnosed in patients with DGF than in those with immediate graft function (50% vs. 39.9%, P<0.05). Length of hospitalization was longer and the number of needle core biopsies was higher in patients with DGF or rejection. The presence of both complications had an additive effect.

CONCLUSIONS

This study showed that DGF did not adversely affect kidney graft survival in patients without rejection. However, it increased the length of hospitalization and the number of graft biopsies, thus increasing the cost of transplantation. Moreover, rejection was more frequent in patients with DGF, and it had a negative impact on graft outcome. Because the association of DGF and rejection gave the poorest outcome, an effort should be made to prevent both complications.

Membranous nephropathy: recurrence after kidney transplantation

BACKGROUND

It is supposed that about 5% of dialysis patients had membranous nephropathy as a cause for their renal failure. Despite of this prevalence, only 33 cases of recurrent membranous nephropathy after kidney transplantation have been reported in the English literature.

METHODS

Among 509 recipients of renal allografts, membranous glomerulonephritis was the cause of renal failure in five patients, who received six transplants.

RESULTS

Recurrence of the disease was observed in three allografts (50%) in three patients, all of them were on treatment with cyclosporin and low-dose prednisone. Proteinuria appeared at 2, 5 and 19 months after grafting. One patient experienced a spontaneous remission after 12 months and he is free from proteinuria and with good renal function after 5 years. The remaining two patients presented progressive renal function deterioration and returned to haemodialysis 24 and 17 months after th appearance of proteinuria. In these patients increasing the immunosuppression did not produce any beneficial effect. One of those patients underwent a second transplant; recurrence of the membranous nephropathy has not been observed after 3 years of follow-up.

CONCLUSIONS

In this study three new cases of recurrence of membranous nephropathy are reported. One patient experienced a spontaneous remission of proteinuria. Recurrence of membranous nephropathy in renal allograft was very high in our series. Its appearance was associated with poor prognosis of the graft in most patients, although spontaneous remission of proteinuria is possible.

Nosocomial measles infection in a pediatric hospital during a community-wide epidemic

From Jan. 1, 1988, through Dec. 31, 1988, a total of 89 cases of measles were observed at Childrens Hospital of Los Angeles, and 37 patients were admitted to the hospital. Of the 37 patients, six were not initially thought to have measles, which resulted in exposure of 107 patients and 24 personnel. Of the exposed patients, measles developed in four. One nosocomially infected infant died of pneumonia. Another exposed patient was subsequently admitted to another hospital with unrecognized measles, which led to exposure of an additional eight patients. Of seven employees in whom measles developed, two required hospitalization because of pneumonia. Two hundred eleven employee days were lost because of measles exposure or infection. Infection control interventions included prophylaxis of exposed patients, employee education, and measles immunization for susceptible personnel. Of 1103 hospital personnel considered susceptible to measles, 800 received monovalent measles vaccine. No secondary cases of measles occurred in hospital personnel who received appropriate prophylaxis. We conclude that infection control programs aimed at mandating measles immunity in hospital employees at risk should be instituted.

Regeneration of growth plate cartilage induced in the neonatal rat hindlimb by reamputation

Following primary hindlimb amputations dividing the lower femur or the central tibiofibula, the neonatal rat innately regenerates the distal growth plate(s) with a frequency of about 20-30%. One or two reamputation procedures were performed in an effort to increase the frequency of physeal regeneration, noting that such procedures, and related forms of tissue stimulation, have been repeatedly shown to induce regenerative growth at limb amputation sites of some amphibians that display little innate regenerative capacity. The present reamputation sequences divided the skeletal stump through the cartilaginous mass arising at its distal end. Following first reamputation an approximate three fold increase in the frequency of growth plate cartilage regeneration was observed at transfemoral and transtibiofibular sites. Only after second reamputation, however, did tibiofibular physeal cartilage regeneration equal in frequency that observed after first reamputation through the lower femur. Ectopic growth plate cell architecture was identified in cartilaginous extensions arising from the side of the distal femoral shaft, and also within the regrown secondary cartilage body, which unites the lower tibia and fibula in the shank of the rat. Moreover, among 3 of 11 femoral amputees that had sustained reamputations, regrowth of the distal femoral condylar mass and profile were achieved to varying degrees. It is concluded that a regimen of reamputation, known to induce regenerative growth in the amphibian limb, also induces skeletal regneration in the mammalian limb, and lead to the appearance of ectopic growth plate cell architecture at adjacent sites.

Nonsuppressible insulin-like activity and somatomedin C levels in normal pregnant women, in pregnant women with gestational diabetes, and in umbilical cord blood of mature and premature infants

This study was undertaken to determine the significance of the changes in nonsuppressible insulin-like activity as measured by the fat pad assay and by the levels of immunoreactive somatomedin C, growth hormone, and human placental lactogen in sera of term normal pregnant women, mothers who delivered prematurely, and women with gestational diabetes at term as compared to normal nonpregnant subjects. These hormones were also measured in the umbilical cord blood of these patients at the time of delivery to determine the possible mechanisms of the fetal growth in utero. Our investigations showed that (1) nonsuppressible insulin-like activity is elevated during pregnancy, but its level was lower in mothers with gestational diabetes in spite of significantly higher serum human placental lactogen compared with normal pregnant mothers; (2) nonsuppressible insulin-like activity is significantly lower in premature infants than in term infants; (3) somatomedin C levels were significantly elevated in pregnant mothers in spite of suppression of growth hormone; (4) nonsuppressible insulin-like activity and somatomedin C levels in infants of mothers with gestational diabetes were not significantly elevated in spite of higher birth weight, indicating that nonsuppressible insulin-like activity and somatomedins are not the only factors responsible for the increase of birth weight of children of diabetic mothers; (5) there was marked discordance between the growth hormone level in the neonates and somatomedin C levels.